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dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

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Well, it's not especially important that target->d_iname get the contents
of dentry->d_iname, but it's important that it get initialized with
*something*, otherwise we're just exposing some random piece of memory to
anyone who reads the link at /proc/<pid>/fd/<fd> for the deleted file, when
it's still held open by someone.

I've run a test program that copies a short (<36 character) name ontop of a
long (>=36 character) name and see that the first time I run it, without
this patch, I get unpredicatable results out of /proc/<pid>/fd/<fd>.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
J. Bruce Fields 2007-10-21 16:41:38 -07:00 • committed by Linus Torvalds
parent b68680e473
commit 321bcf9216
1 changed files with 2 additions and 0 deletions
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fs/dcache.c
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@ -1479,6 +1479,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
* dentry:internal, target:external. Steal target's * dentry:internal, target:external. Steal target's
* storage and make target internal. * storage and make target internal.
*/ */
memcpy(target->d_iname, dentry->d_name.name,
dentry->d_name.len + 1);
dentry->d_name.name = target->d_name.name; dentry->d_name.name = target->d_name.name;
target->d_name.name = target->d_iname; target->d_name.name = target->d_iname;
} }