From: Amir Goldstein amir73il@gmail.com

commit 974e3fe0ac61de85015bbe5a4990cf4127b304b2 upstream.

Encoding file handles is usually performed by a filesystem >encode_fh() method that may fail for various reasons.

The legacy users of exportfs_encode_fh(), namely, nfsd and name_to_handle_at(2) syscall are ready to cope with the possibility of failure to encode a file handle.

There are a few other users of exportfs_encode_{fh,fid}() that currently have a WARN_ON() assertion when ->encode_fh() fails. Relax those assertions because they are wrong.

The second linked bug report states commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") in v6.6 as the regressing commit, but this is not accurate.

The aforementioned commit only increases the chances of the assertion and allows triggering the assertion with the reproducer using overlayfs, inotify and drop_caches.

Triggering this assertion was always possible with other filesystems and other reasons of ->encode_fh() failures and more particularly, it was also possible with the exact same reproducer using overlayfs that is mounted with options index=on,nfs_export=on also on kernels < v6.6. Therefore, I am not listing the aforementioned commit as a Fixes commit.

Backport hint: this patch will have a trivial conflict applying to v6.6.y, and other trivial conflicts applying to stable kernels < v6.6.

Reported-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Tested-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-unionfs/671fd40c.050a0220.4735a.024f.GAE@googl... Reported-by: Dmitry Safonov dima@arista.com Closes: https://lore.kernel.org/linux-fsdevel/CAGrbwDTLt6drB9eaUagnQVgdPBmhLfqqxAf3F... Cc: stable@vger.kernel.org Signed-off-by: Amir Goldstein amir73il@gmail.com Link: https://lore.kernel.org/r/20241219115301.465396-1-amir73il@gmail.com Signed-off-by: Christian Brauner brauner@kernel.org [Minor conflict resolved due to code context change.] Signed-off-by: Jianqi Ren jianqi.ren.cn@windriver.com Signed-off-by: He Zhe zhe.he@windriver.com --- Verified the build test --- fs/notify/fdinfo.c | 4 +--- fs/overlayfs/copy_up.c | 5 ++--- 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index 55081ae3a6ec..dd5bc6ffae85 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -51,10 +51,8 @@ static void show_mark_fhandle(struct seq_file *m, struct inode *inode) size = f.handle.handle_bytes >> 2;

ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, NULL); - if ((ret == FILEID_INVALID) || (ret < 0)) { - WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret); + if ((ret == FILEID_INVALID) || (ret < 0)) return; - }

f.handle.handle_type = ret; f.handle.handle_bytes = size * sizeof(u32); diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 5fc32483afed..c5d8ad610a37 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -366,9 +366,8 @@ struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real, buflen = (dwords << 2);

err = -EIO; - if (WARN_ON(fh_type < 0) || - WARN_ON(buflen > MAX_HANDLE_SZ) || - WARN_ON(fh_type == FILEID_INVALID)) + if (fh_type < 0 || fh_type == FILEID_INVALID || + WARN_ON(buflen > MAX_HANDLE_SZ)) goto out_err;

fh->fb.version = OVL_FH_VERSION;