Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: 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().
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 8232fca738011ca2ec865b46ec721d1796dc0580 before c073d01f6f5367c3a4f07efd507274ed0d03acd0; affected 73049768ad57145acd337102c5aa3c788e6642c8 before 1485a3dd97ab1af2605243cabe6b604546d46dd1; affected 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde before 233a2e190b12884d186027d0b86d43a48799b69c; affected a287620312dc6dcb9a093417a0e589bf30fcf38a before 9dfcadc5e003fb250dd471db90144bd5366140e9; affected a287620312dc6dcb9a093417a0e589bf30fcf38a before 226bd5603371cd9f6642cbb9e9a677f445de3530; affected 43a6281790273c1b0a9ab76609ff0245b968f1e6; affected b6bbb85cf45bf0b070e741997fe0af3a772c5ad5; affected ff4806202749a51938236214adc0281481a57366; affected 74be188eb2dc1c99d63986167b9a67d415fe7326; affected 09a43e81279b8da15526da09877134b8bcf618b0; affected 6.6.144 before 6.6.160; affected 6.12.95 before 6.12.113; affected 6.18.37 before 6.18.56; affected 5.10.260 before 5.11; affected 5.15.211 before 5.16; affected 6.1.177 before 6.2; affected 7.0.14 before 7.1; affected 7.1.2 before 7.2 |
| Linux / Linux | affected 7.2; unaffected 0 before 7.2; unaffected 6.6.160 through 6.6.*; unaffected 6.12.113 through 6.12.*; unaffected 6.18.56 through 6.18.*; unaffected 7.2.10 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/c073d01f6f5367c3a4f07efd507274ed0d03acd0
- https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1
- https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c
- https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9
- https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530