In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix use-after-free in rawdata dedup loop
aa_replace_profiles() walks ns->rawdata_list to dedup the incoming
policy blob against entries already attached to existing profiles.
Per the kernel-doc on struct aa_loaddata, list membership does not
hold a reference: profiles hold pcount, and when the last pcount
drops, do_ploaddata_rmfs() is queued on a workqueue that takes
ns->lock and removes the entry. Between dropping the last pcount
and the workqueue running, an entry remains on the list with
pcount == 0.
aa_get_profile_loaddata() is an unconditional kref_get() on
pcount, so when the dedup loop hits such an entry, refcount
hardening reports
refcount_t: addition on 0; use-after-free.
inside aa_replace_profiles(), and the poisoned counter then
trips "saturated" and "underflow" warnings on the subsequent
uses of the same loaddata.
Before commit a0b7091c4de4 ("apparmor: fix race on rawdata
dereference") the dedup path used a get_unless_zero-style helper
on a single counter, so the existing "if (tmp)" guard was
meaningful. The split-refcount refactor introduced
aa_get_profile_loaddata(), which has plain kref_get() semantics,
and the guard quietly became a no-op.
Introduce aa_get_profile_loaddata_not0(), matching the existing
_not0 convention used by aa_get_profile_not0(), and use it for
the rawdata_list dedup lookup so dying entries are skipped.
Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu
24.04 + stress-ng 0.17.06:
stress-ng --apparmor 1 --klog-check --timeout 60s
Without this patch the three refcount_t warnings fire within a
few seconds. With it the same 60 s run is clean. Coverage is a
smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN
and CONFIG_PROVE_LOCKING would be welcome from anyone with the
cycles.
References
Configurations
Configuration 1 (hide)
|
History
12 Nov 2026, 15:12
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Linux linux Kernel
Linux |
|
| CPE | cpe:2.3:o:linux:linux_kernel:7.0:-:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
|
| References | () https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688 - Patch | |
| References | () https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339 - Patch | |
| References | () https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71 - Patch | |
| References | () https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27 - Patch | |
| References | () https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3 - Patch | |
| References | () https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5 - Patch | |
| References | () https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de - Patch | |
| References | () https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df - Patch | |
| CWE | CWE-416 |
Information
Published : 2026-07-19 12:16
Updated : 2026-11-12 15:12
NVD link : CVE-2026-63827
Mitre link : CVE-2026-63827
CVE.ORG link : CVE-2026-63827
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free