From: Yang Erkun <yangerkun@huawei.com> mainline inclusion from mainline-v6.13-rc1 commit be8f982c369c965faffa198b46060f8853e0f1f0 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBEAMQ CVE: CVE-2024-56558 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active. ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 819 at lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Call Trace: <TASK> e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: bf18f163e89c ("NFSD: Using exp_get for export getting") Cc: stable@vger.kernel.org # 4.20+ Signed-off-by: Yang Erkun <yangerkun@huawei.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Conflicts: fs/nfsd/export.c [Commit ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock") add the definition of cache_get_rcu.] Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- fs/nfsd/export.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c index 170456ba2e0b..20e36bb38554 100644 --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -1220,9 +1220,12 @@ static int e_show(struct seq_file *m, void *p) return 0; } - exp_get(exp); + if (!(kref_get_unless_zero(&(&exp->h)->ref))) + return 0; + if (cache_check(cd, &exp->h, NULL)) return 0; + exp_put(exp); return svc_export_show(m, cd, cp); } -- 2.31.1