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autofs braino fix for do_last()

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It's an analogue of commit 7500c38a (fix the braino in "namei:
massage lookup_slow() to be usable by lookup_one_len_unlocked()").
The same problem (->lookup()-returned unhashed negative dentry
just might be an autofs one with ->d_manage() that would wait
until the daemon makes it positive) applies in do_last() - we
need to do follow_managed() first.

Fortunately, remaining callers of follow_managed() are OK - only
autofs has that weirdness (negative dentry that does not mean
an instant -ENOENT)) and autofs never has its negative dentries
hashed, so we can't pick one from a dcache lookup.

->d_manage() is a bloody mess ;-/

Cc: stable@vger.kernel.org # v4.6
Spotted-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-06-05 00:23:09 -04:00
parent fac7d1917d
commit e6ec03a25f
1 changed files with 4 additions and 4 deletions
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8
fs/namei.c
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@ -3260,6 +3260,10 @@ static int do_last(struct nameidata *nd,
got_write = false; got_write = false;
} }
error = follow_managed(&path, nd);
if (unlikely(error < 0))
return error;
if (unlikely(d_is_negative(path.dentry))) { if (unlikely(d_is_negative(path.dentry))) {
path_to_nameidata(&path, nd); path_to_nameidata(&path, nd);
return -ENOENT; return -ENOENT;
@ -3275,10 +3279,6 @@ static int do_last(struct nameidata *nd,
return -EEXIST; return -EEXIST;
} }
error = follow_managed(&path, nd);
if (unlikely(error < 0))
return error;
seq = 0; /* out of RCU mode, so the value doesn't matter */ seq = 0; /* out of RCU mode, so the value doesn't matter */
inode = d_backing_inode(path.dentry); inode = d_backing_inode(path.dentry);
finish_lookup: finish_lookup: