diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-26 13:04:16 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-08-03 12:42:48 -0700 |
| commit | 601309611a1714cca934161550291dc5553b6b63 (patch) | |
| tree | c6ec21f4417c298dbe6e028086cc5de84174bcad | |
| parent | 6ba8838527eab698d2b252b750cd5743b09c9737 (diff) | |
| download | lwn-601309611a1714cca934161550291dc5553b6b63.tar.gz lwn-601309611a1714cca934161550291dc5553b6b63.zip | |
vfs: fix race in rcu lookup of pruned dentry
Backport of commit 59430262401bec02d415179c43dbe5b8819c09ce
done by Hugh Dickins <hughd@google.com>
Don't update *inode in __follow_mount_rcu() until we'd verified that
there is mountpoint there. Kudos to Hugh Dickins for catching that
one in the first place and eventually figuring out the solution (and
catching a braino in the earlier version of patch).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | fs/namei.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/namei.c b/fs/namei.c index 6ff858c049c0..732a754d536e 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1013,7 +1013,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, * Don't forget we might have a non-mountpoint managed dentry * that wants to block transit. */ - *inode = path->dentry->d_inode; if (!reverse_transit && unlikely(managed_dentry_might_block(path->dentry))) return false; @@ -1027,6 +1026,12 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, path->mnt = mounted; path->dentry = mounted->mnt_root; nd->seq = read_seqcount_begin(&path->dentry->d_seq); + /* + * Update the inode too. We don't need to re-check the + * dentry sequence number here after this d_inode read, + * because a mount-point is always pinned. + */ + *inode = path->dentry->d_inode; } if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) |