| From | Kamal Mostafa <> | Subject | [PATCH 4.2.y-ckt 216/273] namei: ->d_inode of a pinned dentry is stable only for positives | Date | Mon, 7 Mar 2016 14:50:07 -0800 |
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4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@zeniv.linux.org.uk>
commit d4565649b6d6923369112758212b851adc407f0c upstream.
both do_last() and walk_component() risk picking a NULL inode out of dentry about to become positive, *then* checking its flags and seeing that it's not negative anymore and using (already stale by then) value they'd fetched earlier. Usually ends up oopsing soon after that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/namei.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c index 3500b12..1047096 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1745,11 +1745,11 @@ static int walk_component(struct nameidata *nd, int flags) if (err < 0) return err; - inode = d_backing_inode(path.dentry); seq = 0; /* we are already out of RCU mode */ err = -ENOENT; if (d_is_negative(path.dentry)) goto out_path_put; + inode = d_backing_inode(path.dentry); } if (flags & WALK_PUT) @@ -3133,12 +3133,12 @@ retry_lookup: return error; BUG_ON(nd->flags & LOOKUP_RCU); - inode = d_backing_inode(path.dentry); seq = 0; /* out of RCU mode, so the value doesn't matter */ if (unlikely(d_is_negative(path.dentry))) { path_to_nameidata(&path, nd); return -ENOENT; } + inode = d_backing_inode(path.dentry); finish_lookup: if (nd->depth) put_link(nd); -- 2.7.0
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