The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x c898afdc15645efb555acb6d85b484eb40a45409 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024061333-wincing-tackle-2315@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
c898afdc1564 ("9p: add missing locking around taking dentry fid list") b48dbb998d70 ("9p fid refcount: add p9_fid_get/put wrappers") 47b1e3432b06 ("9p: Remove unnecessary variable for old fids while walking from d_parent") cba83f47fc0e ("9p: Track the root fid with its own variable during lookups") b0017602fdf6 ("9p: fix EBADF errors in cached mode") 2a3dcbccd64b ("9p: Fix refcounting during full path walks for fid lookups") beca774fc51a ("9p: fix fid refcount leak in v9fs_vfs_atomic_open_dotl") 6e195b0f7c8e ("9p: fix a bunch of checkpatch warnings") eb497943fa21 ("9p: Convert to using the netfs helper lib to do reads and caching")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From c898afdc15645efb555acb6d85b484eb40a45409 Mon Sep 17 00:00:00 2001 From: Dominique Martinet asmadeus@codewreck.org Date: Tue, 21 May 2024 21:13:36 +0900 Subject: [PATCH] 9p: add missing locking around taking dentry fid list
Fix a use-after-free on dentry's d_fsdata fid list when a thread looks up a fid through dentry while another thread unlinks it:
UAF thread: refcount_t: addition on 0; use-after-free. p9_fid_get linux/./include/net/9p/client.h:262 v9fs_fid_find+0x236/0x280 linux/fs/9p/fid.c:129 v9fs_fid_lookup_with_uid linux/fs/9p/fid.c:181 v9fs_fid_lookup+0xbf/0xc20 linux/fs/9p/fid.c:314 v9fs_vfs_getattr_dotl+0xf9/0x360 linux/fs/9p/vfs_inode_dotl.c:400 vfs_statx+0xdd/0x4d0 linux/fs/stat.c:248
Freed by: p9_fid_destroy (inlined) p9_client_clunk+0xb0/0xe0 linux/net/9p/client.c:1456 p9_fid_put linux/./include/net/9p/client.h:278 v9fs_dentry_release+0xb5/0x140 linux/fs/9p/vfs_dentry.c:55 v9fs_remove+0x38f/0x620 linux/fs/9p/vfs_inode.c:518 vfs_unlink+0x29a/0x810 linux/fs/namei.c:4335
The problem is that d_fsdata was not accessed under d_lock, because d_release() normally is only called once the dentry is otherwise no longer accessible but since we also call it explicitly in v9fs_remove that lock is required: move the hlist out of the dentry under lock then unref its fids once they are no longer accessible.
Fixes: 154372e67d40 ("fs/9p: fix create-unlink-getattr idiom") Cc: stable@vger.kernel.org Reported-by: Meysam Firouzi Reported-by: Amirmohammad Eftekhar Reviewed-by: Christian Schoenebeck linux_oss@crudebyte.com Message-ID: 20240521122947.1080227-1-asmadeus@codewreck.org Signed-off-by: Dominique Martinet asmadeus@codewreck.org
diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c index f16f73581634..01338d4c2d9e 100644 --- a/fs/9p/vfs_dentry.c +++ b/fs/9p/vfs_dentry.c @@ -48,12 +48,17 @@ static int v9fs_cached_dentry_delete(const struct dentry *dentry) static void v9fs_dentry_release(struct dentry *dentry) { struct hlist_node *p, *n; + struct hlist_head head;
p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p)\n", dentry, dentry); - hlist_for_each_safe(p, n, (struct hlist_head *)&dentry->d_fsdata) + + spin_lock(&dentry->d_lock); + hlist_move_list((struct hlist_head *)&dentry->d_fsdata, &head); + spin_unlock(&dentry->d_lock); + + hlist_for_each_safe(p, n, &head) p9_fid_put(hlist_entry(p, struct p9_fid, dlist)); - dentry->d_fsdata = NULL; }
static int v9fs_lookup_revalidate(struct dentry *dentry, unsigned int flags)