Messages in this thread Patch in this message | | | Date | Mon, 01 Aug 2011 16:19:21 -0700 | From | Greg KH <> | Subject | [66/70] vfs: fix race in rcu lookup of pruned dentry |
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2.6.39-stable review patch. If anyone has any objections, please let us know.
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From: Linus Torvalds <torvalds@linux-foundation.org>
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>
--- fs/namei.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/namei.c +++ b/fs/namei.c @@ -1013,7 +1013,6 @@ static bool __follow_mount_rcu(struct na * 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 na 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))
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