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should_follow_link(): validate ->d_seq after having decided to follow

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... otherwise d_is_symlink() above might have nothing to do with
the inode value we've got.

Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-02-27 19:31:01 -05:00
parent d4565649b6
commit a7f775428b
1 changed files with 5 additions and 0 deletions
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5
fs/namei.c
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@ -1712,6 +1712,11 @@ static inline int should_follow_link(struct nameidata *nd, struct path *link,
return 0;
if (!follow)
return 0;
/* make sure that d_is_symlink above matches inode */
if (nd->flags & LOOKUP_RCU) {
if (read_seqcount_retry(&link->dentry->d_seq, seq))
return -ECHILD;
}
return pick_link(nd, link, inode, seq);
}