link_path_walk(): be careful when failing with ENOTDIR
In RCU mode we might end up with dentry evicted just we check
that it's a directory. In such case we should return ECHILD
rather than ENOTDIR, so that pathwalk would be retries in non-RCU
mode.
Breakage had been introduced in commit b18825a
- prior to that
we were looking at nd->inode, which had been fetched before
verifying that ->d_seq was still valid. That form of check
would only be satisfied if at some point the pathname prefix
would indeed have resolved to a non-directory. The fix consists
of checking ->d_seq after we'd run into a non-directory dentry,
and failing with ECHILD in case of mismatch.
Note that all branches since 3.12 have that problem...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
parent
cbfe8fa6cd
commit
97242f99a0
@ -1954,8 +1954,13 @@ OK:
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continue;
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}
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}
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if (unlikely(!d_can_lookup(nd->path.dentry)))
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if (unlikely(!d_can_lookup(nd->path.dentry))) {
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if (nd->flags & LOOKUP_RCU) {
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if (unlazy_walk(nd, NULL, 0))
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return -ECHILD;
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}
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return -ENOTDIR;
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}
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}
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}
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