CVE-2026-89750
Description
In the Linux kernel, the following vulnerability has been resolved: tracing/user_events: Clear copied tracing state before fork duplication dup_task_struct() copies user_event_mm from the parent into the child, without grabbing a reference to it. user_event_mm_dup() should replace it, but it leaves that copied pointer unmodified if user_event_mm_alloc() fails. When the child exits, user_event_mm_remove() decrements a reference the child never owned, which ultimately frees user_event_mm, while the parent still as a stale pointer to it. This creates a UAF, which KASAN reports as: BUG: KASAN: slab-use-after-free in current_user_event_mm+0x51/0x1d0 Write of size 4 at addr ffff888005010d30 by task init/44 Call Trace: <TASK> kasan_report+0xce/0x100 kasan_check_range+0x10f/0x1e0 current_user_event_mm+0x51/0x1d0 user_events_ioctl+0x82e/0x15c0 __x64_sys_ioctl+0x139/0x1c0 do_syscall_64+0xce/0x450 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 44: __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x180/0x3a0 user_event_mm_alloc+0x3c/0x1f0 current_user_event_mm+0x88/0x1d0 Freed by task 42: __kasan_slab_free+0x43/0x70 kfree+0x13a/0x390 process_one_work+0x696/0xf90 worker_thread+0x420/0xba0 The fix simply clears the copied pointer before any possible failure. In case of failure, the child then has nothing to free.
How to fix
- Linux Linux33ce55b368b64d65941867add00e7f288cbb8234, 63b39e49a4c9d68e010e96b26fc7374f0864f2b1, 25a0758cf6bdbfddac2be71124c9bd0692f4b0b1, b799f67119aff179719a0b1e12441ebbdaaf62f9, 390f6bd8583d177029d9df4bea6667509e55a765 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 7235759084a4f8524a46bd2638885ff3b34ce279 ≤ v < 33ce55b368b64d65941867add00e7f288cbb8234, 7235759084a4f8524a46bd2638885ff3b34ce279 ≤ v < 63b39e49a4c9d68e010e96b26fc7374f0864f2b1, 7235759084a4f8524a46bd2638885ff3b34ce279 ≤ v < 25a0758cf6bdbfddac2be71124c9bd0692f4b0b1, 7235759084a4f8524a46bd2638885ff3b34ce279 ≤ v < b799f67119aff179719a0b1e12441ebbdaaf62f9, 7235759084a4f8524a46bd2638885ff3b34ce279 ≤ v < 390f6bd8583d177029d9df4bea6667509e55a765, 6.4 | 33ce55b368b64d65941867add00e7f288cbb8234, 63b39e49a4c9d68e010e96b26fc7374f0864f2b1, 25a0758cf6bdbfddac2be71124c9bd0692f4b0b1, b799f67119aff179719a0b1e12441ebbdaaf62f9, 390f6bd8583d177029d9df4bea6667509e55a765 |
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