[PATCH OLK-6.6 v2 0/2] CVE-2026-23319
Kui-Feng Lee (1): bpf: export bpf_link_inc_not_zero. Lang Xu (1): bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim include/linux/bpf.h | 6 ++++++ kernel/bpf/syscall.c | 3 ++- kernel/bpf/trampoline.c | 4 +--- 3 files changed, 9 insertions(+), 4 deletions(-) -- 2.34.1
From: Kui-Feng Lee <thinker.li@gmail.com> stable inclusion from stable-v6.6.130 commit 4bb55e430d82161206db5c00b9410018ab4f9a36 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13962 CVE: CVE-2026-23319 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 67c3e8353f45c27800eecc46e00e8272f063f7d1 ] bpf_link_inc_not_zero() will be used by kernel modules. We will use it in bpf_testmod.c later. Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com> Link: https://lore.kernel.org/r/20240530065946.979330-5-thinker.li@gmail.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Stable-dep-of: 56145d237385 ("bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- include/linux/bpf.h | 6 ++++++ kernel/bpf/syscall.c | 3 ++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index c9f81962d9f9..d6498fbda50a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2340,6 +2340,7 @@ int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer); int bpf_link_settle(struct bpf_link_primer *primer); void bpf_link_cleanup(struct bpf_link_primer *primer); void bpf_link_inc(struct bpf_link *link); +struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link); void bpf_link_put(struct bpf_link *link); int bpf_link_new_fd(struct bpf_link *link); struct bpf_link *bpf_link_get_from_fd(u32 ufd); @@ -2695,6 +2696,11 @@ static inline void bpf_link_inc(struct bpf_link *link) { } +static inline struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link) +{ + return NULL; +} + static inline void bpf_link_put(struct bpf_link *link) { } diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 042f44a27941..81ab8e889c7d 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5280,10 +5280,11 @@ static int link_detach(union bpf_attr *attr) return ret; } -static struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link) +struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link) { return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? link : ERR_PTR(-ENOENT); } +EXPORT_SYMBOL(bpf_link_inc_not_zero); struct bpf_link *bpf_link_by_id(u32 id) { -- 2.34.1
From: Lang Xu <xulang@uniontech.com> stable inclusion from stable-v6.6.130 commit 9b02c5c4147f8af8ed783c8deb5df927a55c3951 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13962 CVE: CVE-2026-23319 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 56145d237385ca0e7ca9ff7b226aaf2eb8ef368b ] The root cause of this bug is that when 'bpf_link_put' reduces the refcount of 'shim_link->link.link' to zero, the resource is considered released but may still be referenced via 'tr->progs_hlist' in 'cgroup_shim_find'. The actual cleanup of 'tr->progs_hlist' in 'bpf_shim_tramp_link_release' is deferred. During this window, another process can cause a use-after-free via 'bpf_trampoline_link_cgroup_shim'. Based on Martin KaFai Lau's suggestions, I have created a simple patch. To fix this: Add an atomic non-zero check in 'bpf_trampoline_link_cgroup_shim'. Only increment the refcount if it is not already zero. Testing: I verified the fix by adding a delay in 'bpf_shim_tramp_link_release' to make the bug easier to trigger: static void bpf_shim_tramp_link_release(struct bpf_link *link) { /* ... */ if (!shim_link->trampoline) return; + msleep(100); WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline, NULL)); bpf_trampoline_put(shim_link->trampoline); } Before the patch, running a PoC easily reproduced the crash(almost 100%) with a call trace similar to KaiyanM's report. After the patch, the bug no longer occurs even after millions of iterations. Fixes: 69fd337a975c ("bpf: per-cgroup lsm flavor") Reported-by: Kaiyan Mei <M202472210@hust.edu.cn> Closes: https://lore.kernel.org/bpf/3c4ebb0b.46ff8.19abab8abe2.Coremail.kaiyanm@hust... Signed-off-by: Lang Xu <xulang@uniontech.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://patch.msgid.link/279EEE1BA1DDB49D+20260303095217.34436-1-xulang@unio... Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/trampoline.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 08325a65835b..bb842decab0d 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -733,10 +733,8 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog, mutex_lock(&tr->mutex); shim_link = cgroup_shim_find(tr, bpf_func); - if (shim_link) { + if (shim_link && !IS_ERR(bpf_link_inc_not_zero(&shim_link->link.link))) { /* Reusing existing shim attached by the other program. */ - bpf_link_inc(&shim_link->link.link); - mutex_unlock(&tr->mutex); bpf_trampoline_put(tr); /* bpf_trampoline_get above */ return 0; -- 2.34.1
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