openat2 had a bug: if we pass RESOLVE_NO_XDEV, then openat2 doesn't traverse through automounts, but may still trigger them. (See the link for full bug report with reproducer.) This commit fixes this bug. Link: https://lore.kernel.org/linux-fsdevel/20250817075252.4137628-1-safinaskar@xxxxxxxxxxxx/ Fixes: fddb5d430ad9fa91b49b1 ("open: introduce openat2(2) syscall") Reviewed-by: Aleksa Sarai <cyphar@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Askar Safin <safinaskar@xxxxxxxxxxxx> --- fs/namei.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/namei.c b/fs/namei.c index c23e5a076ab3..bfa8232b94dc 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1449,6 +1449,10 @@ static int follow_automount(struct path *path, int *count, unsigned lookup_flags dentry->d_inode) return -EISDIR; + /* No need to trigger automounts if mountpoint crossing is disabled. */ + if (lookup_flags & LOOKUP_NO_XDEV) + return -EXDEV; + if (count && (*count)++ >= MAXSYMLINKS) return -ELOOP; @@ -1472,6 +1476,10 @@ static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped, /* Allow the filesystem to manage the transit without i_rwsem * being held. */ if (flags & DCACHE_MANAGE_TRANSIT) { + if (lookup_flags & LOOKUP_NO_XDEV) { + ret = -EXDEV; + break; + } ret = path->dentry->d_op->d_manage(path, false); flags = smp_load_acquire(&path->dentry->d_flags); if (ret < 0) -- 2.47.2
