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KMSAN reported uninit-value access in __unix_walk_scc() [1].
In the list_for_each_entry_reverse() loop, when the vertex's index
equals it's scc_index, the loop uses the variable vertex as a
temporary variable that points to a vertex in scc. And when the loop
is finished, the variable vertex points to the list head, in this case
scc, which is a local variable on the stack (more precisely, it's not
even scc and might underflow the call stack of __unix_walk_scc():
container_of(&scc, struct unix_vertex, scc_entry)).
However, the variable vertex is used under the label prev_vertex. So
if the edge_stack is not empty and the function jumps to the
prev_vertex label, the function will access invalid data on the
stack. This causes the uninit-value access issue.
Fix this by introducing a new temporary variable for the loop.
[1]
BUG: KMSAN: uninit-value in __unix_walk_scc net/unix/garbage.c:478 [inline]
BUG: KMSAN: uninit-value in unix_walk_scc net/unix/garbage.c:526 [inline]
BUG: KMSAN: uninit-value in __unix_gc+0x2589/0x3c20 net/unix/garbage.c:584
__unix_walk_scc net/unix/garbage.c:478 [inline]
unix_walk_scc net/unix/garbage.c:526 [inline]
__unix_gc+0x2589/0x3c20 net/unix/garbage.c:584
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xade/0x1bf0 kernel/workqueue.c:3312
worker_thread+0xeb6/0x15b0 kernel/workqueue.c:3393
kthread+0x3c4/0x530 kernel/kthread.c:389
ret_from_fork+0x6e/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Uninit was stored to memory at:
unix_walk_scc net/unix/garbage.c:526 [inline]
__unix_gc+0x2adf/0x3c20 net/unix/garbage.c:584
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xade/0x1bf0 kernel/workqueue.c:3312
worker_thread+0xeb6/0x15b0 kernel/workqueue.c:3393
kthread+0x3c4/0x530 kernel/kthread.c:389
ret_from_fork+0x6e/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Local variable entries created at:
ref_tracker_free+0x48/0xf30 lib/ref_tracker.c:222
netdev_tracker_free include/linux/netdevice.h:4058 [inline]
netdev_put include/linux/netdevice.h:4075 [inline]
dev_put include/linux/netdevice.h:4101 [inline]
update_gid_event_work_handler+0xaa/0x1b0 drivers/infiniband/core/roce_gid_mgmt.c:813
CPU: 1 PID: 12763 Comm: kworker/u8:31 Not tainted 6.10.0-rc4-00217-g35bb670d65fc #32
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014
Workqueue: events_unbound __unix_gc
Fixes: 3484f06317 ("af_unix: Detect Strongly Connected Components.")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20240702160428.10153-1-syoshida@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.