Pull tracing fixes from Steven Rostedt:
- Fix use-after-free in eventfs_remove_rec()
The freeing of the eventfs_inode children used list_for_each_entry()
where the child is freed via srcu, but there's still a chance that it
gets freed. It should be using list_for_each_entry_safe().
- Fix eventfs_inode SRCU use of list in freeing
The iterator uses an SRCU protected list walk on the eventfs inodes.
The eventfs inode uses its "list" field in a union with the RCU list
head. When the inode gets added to the SRCU list it immediately
corrupts the list pointer and can cause an issue with the iterator.
Move the RCU list head to be shared with the children list head which
allows the iterator to check the parent inode if is freed before
referencing the child. Have the iterator check the parent "is_freed"
field and break out if it is set. Also add memory barriers to make
sure the ordering is correct.
- Fix various RCU synchronization issues with direct_functions
Updates to direct_functions have some missing RCU protection and
synchronization. Restructure the code a bit to make sure updates to
the direct_functions are protected.
- Remove an unneeded comma from a scope_guard()
There's a spurious comma in a scope_guard(). Remove it.
- Fix race in per CPU buffer swap in the ring buffer
When a per CPU buffer swap happens, it must make sure that it doesn't
occur while a writer is active. Instead it returns an -EBUSY. But
there's a small race window when a writer moves from one sub-buffer
to the next that it resets the "committing" counter. If a swap
happens at that moment, the buffer used for the commit of an event
will not match the buffer the event is actually on. Instead of using
the "committing" counter, use the recursive detection counter that
does not get reset when the writer crosses sub-buffers.
- Fix off-by-one in ftrace_free_mem()
The function ftrace_free_mem() gets an "end_ptr" as a parameter that
is exclusive to the rang to be freed. But its value is used to search
for the records that expects an inclusive value. Subtract one from
the parameter to convert it to an inclusive range.
- Disable resizing of the ring buffer for persistent buffers
Resizing the persistent buffer has undefined behavior. Prevent it
from being resized.
- Disable changing ring buffer subbuf order when resizing is disabled
The ring buffer subbuffer order can not be changed during resizing.
Use that instead of just checking if the buffer is mapped as mapped
buffers also have resizing disabled.
- Initialize subbuf_order of reader pages when they are created
In rb_allocate_cpu_buffer() the bpage->order is not updated to the
current subbuf_order leaving it as zero. This value is used when the
page is freed.
- Fix test_ringbuffer() to test for ERR_PTR before calling
kthread_stop()
The rb_threads[] array is assigned the output of kthread_run_on_cpu()
which could return an ERR_PTR. At the end of the test, all threads in
the array are cleaned up by kthread_stop() passing in the value in
the array if it isn't zero. But if the array contains an ERR_PTR,
kthread_stop() will not be able to handle it properly.
* tag 'trace-v7.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ring-buffer: Fix crash passing ERR_PTR to kthread_stop()
ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer()
ring-buffer: Prevent subbuf order change when resizing is disabled
ring-buffer: Prevent resizing of persistent ring buffer
ftrace: Fix off-by-one fentry site disable in ftrace_free_mem()
ring-buffer: Use current_context for safe per-CPU buffer swap
ftrace: Drop extra comma in trace_buffered_event_enable
ftrace: Protect direct_functions in update_ftrace_direct_mod
ftrace: Protect direct_functions in update_ftrace_direct_del
ftrace: Protect direct_functions in ftrace_find_rec_direct
eventfs: Use children field for rcu head and add memory barriers
eventfs: Fix use-after-free in eventfs_remove_rec()
Pull s390 fixes from Vasily Gorbik:
- Fix potential uninitialized memory reads and buffer overflows from
malformed zcrypt CCA and EP11 requests by properly validating lengths
and payloads
- Fix possible out of bounds accesses in zcrypt EP11 domain handling by
replacing fixed payload layout assumptions with parsing ASN.1 fields
with bounds checks
- Fix zcrypt CCA and EP11 request and reply buffer allocations missing
required 4-byte padding, and scrub the full allocation on release
- Fix zcrypt CCA and EP11 messages leaking up to 3 uninitialized bytes
of memory by zeroing trailing alignment padding
* tag 's390-7.2-7' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
s390/zcrypt: Pad trailing CCA or EP11 message with zeros
s390/zcrypt: Improve EP11 CPRB domain handling with ASN.1 parsing
s390/zcrypt: Improve EP11 CPRB length and overflow checks
s390/zcrypt: Improve CCA CPRB length and overflow checks
s390/zcrypt: Fix CPRB memory allocation in zcrypt misc code
In test_ringbuffer()'s out_free cleanup loop, the check
`!rb_threads[cpu]` only catches NULL entries and misses entries that
hold an ERR_PTR.
rb_threads[] is static, so unassigned slots are NULL. But when
kthread_run_on_cpu() fails for a cpu, it stores ERR_PTR(-ENOMEM) (or
-EINTR) in rb_threads[cpu] before the creation loop jumps to out_free.
That entry is non-NULL, so the old `!ptr` check does not break, and the
cleanup proceeds to call kthread_stop() on the ERR_PTR. kthread_stop()
then dereferences the bogus pointer, crashing the kernel during the
late_initcall self-test.
crash logs:
BUG: kernel NULL pointer dereference, address: 000000000000001c
Oops: 0002 [#1] SMP NOPTI
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 7.2.0-rc6-dirty #7 PREEMPT(lazy)
RIP: 0010:kthread_stop+0x2e/0x220
RBX: fffffffffffffff4
CR2: 000000000000001c
Call Trace:
<TASK>
test_ringbuffer+0x1ec/0x650
do_one_initcall+0x6c/0x2c0
kernel_init_freeable+0x21d/0x420
kernel_init+0x15/0x1c0
ret_from_fork+0x21b/0x320
</TASK>
Kernel panic - not syncing: Fatal exception
Cc: stable@vger.kernel.org
Fixes: 64ed3a049e ("ring-buffer: make use of the helper function kthread_run_on_cpu()")
Link: https://patch.msgid.link/20260807154145.2846521-2-sh_def@163.com
Signed-off-by: Hui Su <sh_def@163.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When a module's init text is freed, do_init_module() calls
ftrace_free_mem() with a half-open [start, end) range. However the
ftrace_cmp_recs() comparator treats the upper bound as inclusive, as all
its other users do, passing 'ip + size - 1'. So ftrace_free_mem() can
delete a record sitting exactly at 'end', which is outside the freed
range.
For a kernel without CFI or IBT, the first record of a function is at
the function start, which for the first function in a module is also the
base of its text allocation. As the module allocator packs its regions,
that address is often the 'end' passed by a neighboring module's
do_init_module(), causing the first function's ftrace location to get
disabled, preventing an attempt to livepatch it:
livepatch: failed to find location for function 'pcspkr_probe'
Convert the exclusive end to the inclusive 'end - 1' the comparator
expects, and return early for an empty range to avoid the subtraction
from underflowing when the init text size is zero.
Cc: stable@vger.kernel.org
Fixes: 42c269c88d ("ftrace: Allow for function tracing to record init functions on boot up")
Link: https://patch.msgid.link/1b5ccfa8095bdb1277f84af1c2c2e2205aca03ae.1785992188.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring_buffer_swap_cpu() function currently checks the per-CPU
committing counter to determine if a buffer is actively being written to
before performing the swap. However, there exists a race window where
this check can be bypassed:
ring_buffer_lock_reserve
cpu_buffer = buffer->buffers[cpu]; // cpu_buffer_a
rb_reserve_next_event
rb_start_commit // inc committing
if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {...}
__rb_reserve_next
rb_move_tail
rb_end_commit(cpu_buffer); // dec committing => 0
/* interrupt hits here, successfully swaps! */
local_inc(&cpu_buffer->committing);
ring_buffer_unlock_commit
cpu_buffer = buffer->buffers[cpu]; // cpu_buffer_b
rb_commit
rb_end_commit
RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))
// triggers warning
The committing counter can temporarily drop to 0 during a single write
operation (within rb_move_tail), creating a window where swap can
succeed even though the write is still in progress. This leads to
inconsistent buffer state and triggers the RB_WARN_ON in rb_commit().
Replace the committing counter check with current_context checks, which
are set at the entry of ring_buffer_lock_reserve() and remain valid
throughout the entire write operation, providing a reliable indicator of
buffer busy state during swap.
Cc: stable@vger.kernel.org
Fixes: 4239c38fe0 ("ring-buffer: Process commits whenever moving to a new page.")
Link: https://patch.msgid.link/20260803005640.2445666-2-wutengda@huaweicloud.com
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Pull x86 fix from Ingo Molnar:
- Fix MCE CMCI discovery initialization ordering bug (Breno Leitao)
* tag 'x86-urgent-2026-08-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mce: Set up the polling timer before CMCI discovery
Pull futex fix from Ingo Molnar:
- Fix race in futex_pivot_pending() during private hash resize
that can cause stuck tasks (Yao Kai)
* tag 'locking-urgent-2026-08-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Fix race in futex_pivot_pending() during private hash resize
Pull USB / Thunderbolt fixes from Greg KH:
"Here are some small USB and Thunderbolt driver fixes for 7.2-rc7 that
resolve some reported issues. Included in here are:
- new quirk for some broken USB devices
- thunderbolt device fixes for reported issues
- usb gadget driver fix
- usb atm driver fix
- xhci driver fixes.
- other minor USB driver fixes
All of these have been in linux-next this week with no reported
issues"
* tag 'usb-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
usb: xhci: use BIT_ULL for CRCR bits to fix incorrect 64bit mask
usb: quirks: Add ShanWan gamepad to quirk list
usb: hub: Split announce_device() to log device identity before enumeration
usb: core: Add quirk for 255-bytes initial config read
usb: atm: cxacru: properly kill rcv_urb on error in cxacru_cm()
usb: misc: usbio: check ibuf_len against rxbuf_len in bulk msg
usb: gadget: f_ncm: Use unsigned int for ndp_index
usb: cdnsp: fix incorrect endian conversions for APB timeout register
thunderbolt: Initialize ->domain_released completion before it is being used
thunderbolt: icm: Preserve USB4 proxy data-valid bit
thunderbolt: Bound the DROM dual link port number before indexing sw->ports
thunderbolt: Fix bandwidth group reservation indexing
thunderbolt: stream: Unmap buffers with mapped size
Pull tty / serial / vt driver fixes from Greg KH:
"Here are some small serial and vt tty driver fixes for 7.2-rc7 that
resolve some reported problems. Included in here are:
- two vt core fixes
- amba-pl011 serial driver fixes
- 8250_of and 8250_dma driver fixes
- qcom-geni serial driver fix
- sc16is7xx serial driver fix
All of these have been in linux-next this week with no reported
issues"
* tag 'tty-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
serial: amba-pl011: synchronize DMA teardown
serial: amba-pl011: cancel RS485 hrtimers after freeing IRQ
serial: amba-pl011: fix indefinite RS485 post-send delay
vt: add permission check for KDSKBMETA ioctl
vt: stabilize tty reference in kbd_keycode with tty_port_tty_get
serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx
serial: qcom-geni: fix TX DMA buffer flush
serial: 8250_dma: Clear stale RX state on shutdown
serial: sc16is7xx: enable THRI before filling TX FIFO
Pull staging driver fixes from Greg KH:
"Here are some more small staging driver fixes, just for the rtl8723bs
driver, for some reported problems found with it now that people are
starting to actually test the thing with "bad" networks.
Nothing major, but good to have in the -final release. All of these
have been in linux-next for over a week with no reported problems"
* tag 'staging-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
staging: rtl8723bs: validate monitor transmit frame lengths
staging: rtl8723bs: fix missing shared-key auth challenge length check
staging: rtl8723bs: fix OOB read in WMM_param_handler()
staging: rtl8723bs: fix OOB read in rtw_get_wpa_ie()
Pull char / misc and documentation fixes from Greg KH:
"Here are some small char/misc and nvmem and documentation fixes for
7.2-rc7 to resolve some reported issues. Included in here are:
- updates to the documentation for the kernel threat model and
security bugs to get the LLMs to actually follow what we have been
asking them to do (i.e. not claim security issues for things we do
not consider security issues.)
- nvmem driver fixes which required a tiny "layout" driver to be
added.
- fastrpc driver fixes
- mei driver fix
- counter driver fix
- binder driver fix
All of these have been in linux-next this week with no reported
problems"
* tag 'char-misc-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
docs: security-bugs: clarify some mandatory steps for AI reports
docs: coding-assistant: explain important steps when looking for bugs
docs: security-bugs: clarify what counts as a valid version
docs: threat-model: move fake devices out of "non production use"
docs: threat-model: clarify "security bug" vs "vulnerability"
counter: microchip-tcb-capture: Fix DT channel validation
mei: pull kvfree out of spinlock
rust_binder: do not query current thread for all ioctls
nvmem: layouts: Add fixed-layout driver
nvmem: apple-spmi-nvmem: wrap regmap calls to satisfy CFI
misc: fastrpc: fix memory leak in fastrpc_channel_ctx_free
misc: fastrpc: fix channel ctx ref leak when session alloc fails
misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke
misc: fastrpc: Remove buffer from list prior to unmap operation
misc: fastrpc: Fix initial memory allocation for Audio PD memory pool
Pull fbdev fixes from Helge Deller:
"A few patches for the core fbdev layer which stabilize or fix
potential issues with text font rendering after screen rotation or
after user initiated font changes and locking fixes for sysfb during
modifications of the graphics mode database"
* tag 'fbdev-for-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev:
fbdev: bitblit: bound-check glyph index in bit_cursor()
fbdev: Fix out-of-bounds access when rotating console after font resize
fbdev: core: Fix pointer desynchronization in fb_io_read()
fbdev: serialize mode sysfs access with lock_fb_info()
fbdev: clear fb_info->mode before deleting a videomode
fbdev: bound mode sysfs output to the sysfs buffer
When an eventfs inode is freed, it sets ei->is_freed and then uses its
ei->list to add it to the srcu link list as the list field is a union with
the rcu list head. As the ei->list is used to iterate over an SRCU
protected list without taking the eventfs_mutex, there's nothing stopping
the iteration over that list to see the ei->rcu instead of the ei->list
and it will read a corrupt target.
To fix this, change the union of the rcu list head with the children list.
On freeing the eventfs inode, set the is_free and execute a smp_wmb()
before adding the eventfs inode to the SRCU list.
On iteration of the ei->children list, at the start, execute a smp_rmb()
and then read the is_freed of the ei to see if the children list is still
valid. If is_freed is set, then the ei_child read is not valid and the
loop should exit immediately.
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260808094215.4252430d@robin
Fixes: 704f960dbe ("eventfs: Read ei->entries before ei->children in eventfs_iterate()")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260806022719.375354-1-shuangpeng.kernel%40gmail.com
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
eventfs_remove_rec() recursively removes the child at the current loop
position. After the recursive call returns, list_for_each_entry() advances
by reading list.next from the removed child.
If free_ei() drops the final reference, release_ei() reuses the list/rcu
union to queue an SRCU callback. The child may be freed before that read.
The eventfs_mutex serializes list updates, but it does not keep the removed
child alive or prevent the SRCU callback from running.
Use list_for_each_entry_safe() to save the next sibling before recursively
removing the current child.
Cc: stable@vger.kernel.org
Fixes: 43aa6f97c2 ("eventfs: Get rid of dentry pointers without refcounts")
Link: https://patch.msgid.link/20260806022719.375354-1-shuangpeng.kernel@gmail.com
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Pull driver core fixes from Danilo Krummrich:
- Fix Rust build failure on s390 by gating ioremap() / iounmap()
helpers and the io::mem module on CONFIG_HAS_IOMEM; gate affected
doctests as well.
- Add missing kernel-doc for show_const / store_const union members in
struct device_attribute.
* tag 'driver-core-7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core:
rust: io: gate ioremap doctests on CONFIG_HAS_IOMEM
rust: io: gate ioremap/iounmap on CONFIG_HAS_IOMEM
driver core: add missing kernel-doc for union members
Pull input updates from Dmitry Torokhov:
- Fixes for information leaks and OOB accesses across several drivers,
including evdev, focaltech, edt-ft5x06, iforce, and cs40l50-vibra
- Improvements to the synaptics-rmi4 driver to properly handle F54
worker errors and prevent buffer overflows
- Input validation fixes in the hynitron_cstxxx touchscreen driver to
prevent issues with invalid finger IDs and touch counts
- Fixes for use-after-free and initialization bugs in the byd mouse and
psxpad-spi drivers
- New quirks for the atkbd driver to make keyboard work on HONOR and
Xiaomi laptops
- Support for the ZENAIM LEVERLESS controller in the xpad driver.
* tag 'input-for-v7.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
Input: evdev - sanitize event type index when fetching event masks
Input: synaptics-rmi4 - propagate F54 worker errors to V4L2 queue
Input: synaptics-rmi4 - block s_input when F54 queue is busy
Input: synaptics-rmi4 - bound the F54 report size to the allocated buffer
Input: synaptics-rmi4 - zero report size on F54 work error
Input: synaptics-rmi4 - fix F55 transmitter electrode count typo
Input: hynitron_cstxxx - validate touch count and finger IDs
Input: evdev - fix information leak in evdev_pass_values()
fixp-arith: convert comments to kernel-doc format
Input: focaltech - fix array out-of-bounds in focaltech_process_rel_packet
Input: atkbd - skip deactivate for HONOR ZQC-P
Input: atkbd - skip deactivate for Xiaomi Book Pro 14's internal keyboard
Input: iforce - validate input packet lengths
Input: psxpad-spi - set driver data before use
Input: cs40l50-vibra - validate custom data from user space
Input: xpad - add support for ZENAIM LEVERLESS
Input: edt-ft5x06 - ignore contacts with an out-of-range slot id
Input: byd - synchronize timer deletion before freeing private data
Pull powerpc fixes from Madhavan Srinivasan:
- A couple of fixes for a memory leak and a underflow case
Thanks to George Wilson and R Nageswara Sastry
* tag 'powerpc-7.2-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/pseries: lparcfg - fix kbuf[] underflow
powerpc/pseries: pci - logic bug
powerpc/pseries: papr-phy-attest - validate cmd.length, plug mem leak
bit_cursor() fetches the glyph under the cursor with
c = scr_readw(vc_pos);
src = vc_font.data + ((c & charmask) * w * height);
where charmask is 0x1ff when vc_hi_font_mask is set. The screen buffer
value comes directly from scr_readw() and may be larger than the current
font's glyph count.
Syzkaller triggers this via vcs_write(). The Call Trace shows
vcs_write() in vc_screen.c writing an arbitrary 16-bit value with
writev() to /dev/vcsa, which vcs_write_buf() in vc_screen.c stores via
vcs_scr_writew() without checking charcount. The stored value is later
read in bit_cursor() in bitblit.c.
When the font is changed from a font with 512 glyphs to a font with
256 glyphs, the screen buffer can retain characters with the high
bit set from the previous mode, which could also produce the same
out-of-bounds access.
BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
Read of size 16 at addr ffff800086c57970
Call Trace:
soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365
fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427
hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883
update_region+0x100/0x18c drivers/tty/vt/vt.c:669
vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685
bit_putcs_aligned() and bit_putcs_unaligned() already clamp the glyph
index to vc_font.charcount. Apply the same clamp in bit_cursor() after
extracting the attribute and masking, before indexing fontdata.
The fix completes the bounds checking started in commit 18c4ef4e76
("fbdev: bitblit: bound-check glyph index in bit_putcs*"), which missed
the cursor path.
This change should be safe because the clamp reuses the existing
contract from fbcon: charcount is maintained under console_lock in
con_font_set() and fbcon_font_set(), and hi_font_mask is cleared when
switching from 512 to 256 glyphs. When stale screen data with high bits
remains after a font switch, or when vcs_write() stores an arbitrary
value, clamping the index to 0 prevents the out-of-bounds read without
changing cursor semantics — the same fallback bit_putcs uses.
Reported-by: syzbot+61b1db46218109869c14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=61b1db46218109869c14
Link: https://lore.kernel.org/all/6a75205c.01d0871a.3a0d52.0032.GAE@google.com/
Fixes: 18c4ef4e76 ("fbdev: bitblit: bound-check glyph index in bit_putcs*")
Cc: stable@vger.kernel.org
Assisted-by: Hermes:muse-spark-1.2 syzkaller
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Helge Deller <deller@gmx.de>
[BUG]
Recently, we encountered a KASAN warning as follows:
BUG: KASAN: slab-out-of-bounds in ccw_putcs+0x8bd/0xa80
Read of size 1 at addr ff11000110067100 by task bash/1209
CPU: 10 UID: 0 PID: 1209 Comm: bash Not tainted 7.2.0-rc3 #69 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
Call Trace:
<TASK>
...
kasan_report+0xf0/0x120
? ccw_putcs+0x8bd/0xa80
ccw_putcs+0x8bd/0xa80
? __pfx_ccw_putcs+0x10/0x10
fbcon_putcs+0x338/0x410
? __pfx_ccw_putcs+0x10/0x10
do_update_region+0x21d/0x450
invert_screen+0x29d/0x5e0
? __kmalloc_noprof+0x493/0x640
? vc_do_resize+0x17c/0xe50
clear_selection+0x4c/0x60
vc_do_resize+0xaee/0xe50
fbcon_modechanged+0x2bd/0x640
rotate_all_store+0x298/0x380
...
reproduce:
1) issue two ioctls: first a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,
op.width = 1 and op.height = 1, then a TIOCL_SETSEL ioctl
2) echo 2 > /sys/devices/virtual/graphics/fbcon/rotate_all
3) issue two ioctls: first a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,
op.width = 8 and op.height = 1, then a TIOCL_SETSEL ioctl
4) echo 3 > /sys/devices/virtual/graphics/fbcon/rotate_all
[CAUSE]
The root cause is that fbcon_modechanged() first sets the current rotate's
corresponding ops. Subsequently, during vc_resize(), it may trigger
clear_selection(), and in fbcon_putcs->ccw_putcs[rotate=3], this can result
in an out-of-bounds access to "src". This happens because par->rotated.buf
is reallocated in fbcon_rotate_font():
1) When rotate=2, its size is (width + 7) / 8 * height
2) When rotate=3, its size is (height + 7) / 8 * width
And the call to fbcon_rotate_font() occurs after clear_selection(). In
other words, the fontbuffer is allocated using the size calculated from the
previous rotation 2, but before reallocating it with the new size,
con_putcs is already using the new rotation 3:
rotate_all_store
fbcon_rotate_all
fbcon_set_all_vcs
fbcon_modechanged
set_blitting_type
...
par->bitops = &ccw_fbcon_bitops
vc_resize
...
clear_selection
highlight
...
do_update_region
fbcon_putcs
...
image.dy = vyres - ((xx + count) * vc->vc_font.width) [1] // overflow!
ccw_putcs_aligned
// old buf size is still being used during the read!
src = par->rotated.buf + (scr_readw(s--) & charmask) * cellsize
fb_pad_aligned_buffer----[src KASAN!!!] [2]
info->fbops->fb_imageblit(info, image)
sys_imageblit
fb_imageblit
fb_address_forward
// offset: image->dy * bits_per_line + image->dx * bpp
unsigned int bits = (unsigned int)adr->bits + offset
adr->address += (bits & ~(BITS_PER_LONG - 1u)) / BITS_PER_BYTE [3]
fb_bitmap_imageblit
...
fb_read_offset // page fault! [4]
update_screen
redraw_screen
...
ccw_cursor
soft_cursor
memcpy(src, image->data, dsize)----[src KASAN again!!!] [5]
fbcon_switch
fbcon_rotate_font
font_data_rotate
dst = kmalloc_array(charcount, d_cellsize, GFP_KERNEL)
// the new size is allocated only here!
par->rotated.buf = buf [6]
[FIX]
A fairly obvious approach is to follow fbcon_switch(): in
fbcon_modechanged(), call rotate_font() before vc_resize() so that a
correctly sized buffer is allocated in time, as done in [6]. This fix is
necessary, but it is not sufficient on its own.
In [1] it causes an image.dy overflow (ccw_putcs: vyres = 768,
image.dy = 4294967040), because vc_cols has not been updated in time at
this point (it is likewise only updated after clear_selection()). This
allows (xx + count) * width to exceed vyres, causing image.dy to overflow.
Subsequently, address in [3] is incremented by an even larger amount, which
triggers a page fault at [4].
Therefore, a second fix is required in combination with the first: move
clear_selection() earlier, before set_blitting_type() in
fbcon_set_all_vcs(), to prevent the out-of-bounds access. fbcon_rotate()
has a similar problem, so add the same clear there. Since vc_is_sel() is
not exported, the fbdev side is currently forced to call clear_selection()
unconditionally, causing the global selection to be cleared prematurely.
And this will not cause any other significant impact.
Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Signed-off-by: Helge Deller <deller@gmx.de>
In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to
a faulty user buffer), the loop adjusts the chunk size 'c' and updates
the remaining 'count'. However, the hardware 'src' pointer has already
been eagerly advanced by the original chunk size.
If the loop is allowed to continue, the read will resume from an
incorrect, over-advanced offset. Since the remaining 'count' was only
decremented by the successful bytes, this desynchronization causes the
next iterations to execute more hardware reads than originally bounded,
eventually leading to out-of-bounds I/O reads.
Fix this by breaking out of the loop immediately upon a partial
copy_to_user(). A partial copy indicates a faulty user buffer, making
subsequent read attempts futile. Breaking out ensures we return the
number of successfully read bytes without risking out-of-bounds hardware
accesses in subsequent mismatched iterations.
Fixes: 6121cd9ef9 ("fbdev: Move I/O read and write code into helper functions")
Cc: stable@vger.kernel.org
Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn>
Signed-off-by: Helge Deller <deller@gmx.de>
show_mode(), show_modes(), and store_mode() access fb_info->modelist
and fb_info->mode without holding lock_fb_info(). store_modes() takes
lock_fb_info() while replacing the modelist and freeing the old one.
A concurrent reader or writer can load a pointer to an old modelist
entry before store_modes() frees it, then dereference freed memory or
store a stale freed pointer in fb_info->mode.
Take lock_fb_info() in show_mode(), show_modes(), and store_mode() to
serialize with store_modes(). In show_mode(), copy the mode to the
stack and format after dropping the lock. In store_mode(), split
activate() into a _locked variant to avoid double-locking, and hold
the locks for the modelist walk, mode conversion, activation, and
fb_info->mode assignment together.
Cc: stable@vger.kernel.org # v7.1+
Signed-off-by: Melbin K Mathew <mlbnkm1@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
fb_set_var() can delete a mode from info->modelist when userspace
passes FB_ACTIVATE_INV_MODE through FBIOPUT_VSCREENINFO. The code
checks that the mode being deleted is not the current info->var and
that fbcon is not using it, but it does not check fb_info->mode.
fb_info->mode may still point into the modelist entry being deleted.
If the entry is freed, later mode sysfs reads through show_mode() can
dereference a stale pointer.
Clear fb_info->mode before calling fb_delete_videomode() when it
matches the mode being removed.
Cc: stable@vger.kernel.org # v7.1+
Signed-off-by: Melbin K Mathew <mlbnkm1@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
mode_string() uses snprintf() which can return a value larger than the
remaining buffer space. show_modes() accumulates the return value into i
without checking whether i has reached PAGE_SIZE, causing the offset to
advance past the sysfs buffer if the modelist is long enough.
Add a size parameter to mode_string() and use scnprintf() to return
only the bytes actually written. Add an early return when offset
already exceeds the buffer. In show_modes(), stop accumulating once
the buffer is full.
Cc: stable@vger.kernel.org # v7.1+
Signed-off-by: Melbin K Mathew <mlbnkm1@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
In lparcfg_write(), a count of 0 results in kbuf[] being indexed at -1.
Check for count == 0 in the existing check for count > sizeof(kbuf) and
return -EINVAL if true.
Fixes: 74422e2b19 ("powerpc/pseries: Remove VLA from lparcfg_write()")
Acked-by: Nayna Jain <nayna@linux.ibm.com>
Tested-by: R Nageswara Sastry <rnsastry@linux.ibm.com>
Cc: stable@vger.kernel.org # 4.20
Signed-off-by: George Wilson <gcwilson@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
