CVE-2026-63827 - Vulnerability Details

Vendors	Products
Linux	Linux Kernel

Link	Providers
https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688
https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339
https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27
https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3
https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de
https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df

Type	Values Removed	Values Added
Description		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.
Title		apparmor: fix use-after-free in rawdata dedup loop
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688 https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339 https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27 https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3 https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df

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Between dropping the last pcount\nand the workqueue running, an entry remains on the list with\npcount == 0.\n\naa_get_profile_loaddata() is an unconditional kref_get() on\npcount, so when the dedup loop hits such an entry, refcount\nhardening reports\n\n refcount_t: addition on 0; use-after-free.\n\ninside aa_replace_profiles(), and the poisoned counter then\ntrips \"saturated\" and \"underflow\" warnings on the subsequent\nuses of the same loaddata.\n\nBefore commit a0b7091c4de4 (\"apparmor: fix race on rawdata\ndereference\") the dedup path used a get_unless_zero-style helper\non a single counter, so the existing \"if (tmp)\" guard was\nmeaningful. The split-refcount refactor introduced\naa_get_profile_loaddata(), which has plain kref_get() semantics,\nand the guard quietly became a no-op.\n\nIntroduce aa_get_profile_loaddata_not0(), matching the existing\n_not0 convention used by aa_get_profile_not0(), and use it for\nthe rawdata_list dedup lookup so dying entries are skipped.\n\nReproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu\n24.04 + stress-ng 0.17.06:\n\n stress-ng --apparmor 1 --klog-check --timeout 60s\n\nWithout this patch the three refcount_t warnings fire within a\nfew seconds. With it the same 60 s run is clean. Coverage is a\nsmoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN\nand CONFIG_PROVE_LOCKING would be welcome from anyone with the\ncycles."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["security/apparmor/include/policy_unpack.h", "security/apparmor/policy.c"], "versions": [{"version": "6b6ba87579c7e7c669e0bec91823e7fb693bc5df", "lessThan": "a7a2890028f16e5b0af0bb005d80fcb32559cca3", "status": "affected", "versionType": "git"}, {"version": "6ef1f2926c41ab96952d9696d55a052f1b3a9418", "lessThan": "15fd83a1e42ede15070968806bb6c8b1a5170688", "status": "affected", "versionType": "git"}, {"version": "f9761add6d100962a23996cb68f3d6abdd4d1815", "lessThan": "ce261a20b41db522e320a41bbf1292bf85af66df", "status": "affected", "versionType": "git"}, {"version": "af782cc8871e3683ddd5a3cd2f7df526599863a9", "lessThan": "c3ca2631073b2cef06824fd2bfc452ff7a1023de", "status": "affected", "versionType": "git"}, {"version": "a0b7091c4de45a7325c8780e6934a894f92ac86b", "lessThan": "5e34fa9f6f7cd688ae153fff13139a5cf2d42339", "status": "affected", "versionType": "git"}, {"version": "a0b7091c4de45a7325c8780e6934a894f92ac86b", "lessThan": "6f060496d03e4dc560a40f73770bd08335cb7a27", "status": "affected", "versionType": "git"}, {"version": "3b8e77c7abab40e6de9ad9de730d77984a498840", "status": "affected", "versionType": "git"}, {"version": "d9d8560b9b7932f8cffc4c068c14289220900f79", "status": "affected", "versionType": "git"}, {"version": "763e838adc3c7ec5a7df2990ce84cad951e42721", "status": "affected", "versionType": "git"}, {"version": "6.1.169", "lessThan": "6.1.177", "status": "affected", "versionType": "semver"}, {"version": "6.6.130", "lessThan": "6.6.144", "status": "affected", "versionType": "semver"}, {"version": "6.12.77", "lessThan": "6.12.95", "status": "affected", "versionType": "semver"}, {"version": "6.18.18", "lessThan": "6.18.38", "status": "affected", "versionType": "semver"}, {"version": "5.10.253", "lessThan": "5.11", "status": "affected", "versionType": "semver"}, {"version": "5.15.203", "lessThan": "5.16", "status": "affected", "versionType": "semver"}, {"version": "6.19.8", "lessThan": "6.20", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["security/apparmor/include/policy_unpack.h", "security/apparmor/policy.c"], "versions": [{"version": "7.0", "status": "affected"}, {"version": "0", "lessThan": "7.0", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.177", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.144", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.38", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.3", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2-rc1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.169", "versionEndExcluding": "6.1.177"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.130", "versionEndExcluding": "6.6.144"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.77", "versionEndExcluding": "6.12.95"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": 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