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namei: ->d_inode of a pinned dentry is stable only for positives

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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...

Cc: stable@vger.kernel.org # v3.13+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-02-27 19:23:16 -05:00
parent c80567c82a
commit d4565649b6
1 changed files with 2 additions and 2 deletions
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4
fs/namei.c
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@ -1743,11 +1743,11 @@ 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)
@ -3192,12 +3192,12 @@ static int do_last(struct nameidata *nd,
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);