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| author | Yi Yang <yiyang13@huawei.com> | 2026-09-01 11:31:31 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-10-01 11:15:09 +0200 |
| commit | 226bd5603371cd9f6642cbb9e9a677f445de3530 (patch) | |
| tree | 95cefdfa8fd5d00fb0ee0e1979cd616f3a1deef2 /lib/zstd/common/debug.c | |
| parent | d9feaa93328a6f885afb8ac6374897fafc294222 (diff) | |
| download | linux-stable-226bd5603371cd9f6642cbb9e9a677f445de3530.tar.gz linux-stable-226bd5603371cd9f6642cbb9e9a677f445de3530.zip | |
vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF
The reload of 'vc' added by commit 8fb9ea65c9d1 ("vc_screen: reload load
of struct vc_data pointer in vcs_write() to avoid UAF") sits after the
'if (ret)' block, so the copy-failure break path exits the loop without
reloading vc. If the vc was kfree()'d via vc_port_destruct during the
unlocked copy_from_user() window, the post-loop
'if (written && vc) vcs_scr_updated(vc)' is reached with a stale
non-NULL vc. The '&& vc' guard from commit a287620312dc ("vc_screen:
fix null-ptr-deref in vcs_notifier() during concurrent vcs_write") only
handles the NULL case, not this stale-non-NULL case; vcs_notifier() then
reads param->vc->vc_num from freed memory:
BUG: KASAN: slab-use-after-free in vcs_notifier+0x7c/0xd0
Read of size 2 at addr ffff888007149190
Call Trace:
vcs_notifier+0x7c/0xd0
atomic_notifier_call_chain+0x70/0xa0
vcs_scr_updated+0x77/0xa0
vcs_write+0x71b/0x7e0
Allocated by task: vc_allocate -> con_install -> tty_open
Freed by task: kfree <- vt_ioctl (VT_DISALLOCATE -> vc_port_destruct)
Move the reload to immediately after console_lock(), before 'if (ret)',
so every break path below passes a fresh vc to the post-loop
vcs_scr_updated().
Fixes: a287620312dc ("vc_screen: fix null-ptr-deref in vcs_notifier() during concurrent vcs_write")
Cc: stable@kernel.org
Signed-off-by: Yi Yang <yiyang13@huawei.com>
Link: https://patch.msgid.link/20260901113131.2760010-1-yiyang13@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/zstd/common/debug.c')
0 files changed, 0 insertions, 0 deletions