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Commitdde634057d("xhci: Fix use-after-free in xhci debugfs") causes a null pointer dereference while fixing xhci-debugfs usage of ring pointers that were freed during hibernate. The fix passed addresses to ring pointers instead, but forgot to do this change for the xhci_ring_trb_show function. The address of the ring pointer passed to xhci-debugfs was of a temporary ring pointer "new_ring" instead of the actual ring "ring" pointer. The temporary new_ring pointer will be set to NULL later causing the NULL pointer dereference. This issue was seen when reading xhci related files in debugfs: cat /sys/kernel/debug/usb/xhci/*/devices/*/ep*/trbs [ 184.604861] BUG: unable to handle kernel NULL pointer dereference at (null) [ 184.613776] IP: xhci_ring_trb_show+0x3a/0x890 [ 184.618733] PGD 264193067 P4D 264193067 PUD 263238067 PMD 0 [ 184.625184] Oops: 0000 [#1] SMP [ 184.726410] RIP: 0010:xhci_ring_trb_show+0x3a/0x890 [ 184.731944] RSP: 0018:ffffba8243c0fd90 EFLAGS: 00010246 [ 184.737880] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000000295d6 [ 184.746020] RDX: 00000000000295d5 RSI: 0000000000000001 RDI: ffff971a6418d400 [ 184.754121] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 184.762222] R10: ffff971a64c98a80 R11: ffff971a62a00e40 R12: ffff971a62a85500 [ 184.770325] R13: 0000000000020000 R14: ffff971a6418d400 R15: ffff971a6418d400 [ 184.778448] FS: 00007fe725a79700(0000) GS:ffff971a6ec00000(0000) knlGS:0000000000000000 [ 184.787644] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 184.794168] CR2: 0000000000000000 CR3: 000000025f365005 CR4: 00000000003606f0 [ 184.802318] Call Trace: [ 184.805094] ? seq_read+0x281/0x3b0 [ 184.809068] seq_read+0xeb/0x3b0 [ 184.812735] full_proxy_read+0x4d/0x70 [ 184.817007] __vfs_read+0x23/0x120 [ 184.820870] vfs_read+0x91/0x130 [ 184.824538] SyS_read+0x42/0x90 [ 184.828106] entry_SYSCALL_64_fastpath+0x1a/0x7d Fixes:dde634057d("xhci: Fix use-after-free in xhci debugfs") Cc: <stable@vger.kernel.org> # v4.15 Signed-off-by: Zhengjun Xing <zhengjun.xing@linux.intel.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.