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cifs: check for NULL last_entry before calling cifs_save_resume_key 

Prior to commit eaf35b1, cifs_save_resume_key had some NULL pointer
checks at the top. It turns out that at least one of those NULL
pointer checks is needed after all.

When the LastNameOffset in a FIND reply appears to be beyond the end of
the buffer, CIFSFindFirst and CIFSFindNext will set srch_inf.last_entry
to NULL. Since eaf35b1, the code will now oops in this situation.

Fix this by having the callers check for a NULL last entry pointer
before calling cifs_save_resume_key. No change is needed for the
call site in cifs_readdir as it's not reachable with a NULL
current_entry pointer.

This should fix:

    https://bugzilla.redhat.com/show_bug.cgi?id=750247

Cc: stable@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Reported-by: Adam G. Metzler <adamgmetzler@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Jeff Layton 2011-12-01 20:23:34 -05:00 committed by Steve French
parent 95edcff497
commit 7023676f9e
1 changed files with 8 additions and 2 deletions
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10
fs/cifs/readdir.c
View File

@ -554,7 +554,10 @@ static int find_cifs_entry(const int xid, struct cifs_tcon *pTcon,
rc); rc);
return rc; return rc;
} }
cifs_save_resume_key(cifsFile->srch_inf.last_entry, cifsFile); /* FindFirst/Next set last_entry to NULL on malformed reply */
if (cifsFile->srch_inf.last_entry)
cifs_save_resume_key(cifsFile->srch_inf.last_entry,
cifsFile);
} }
while ((index_to_find >= cifsFile->srch_inf.index_of_last_entry) && while ((index_to_find >= cifsFile->srch_inf.index_of_last_entry) &&
@ -562,7 +565,10 @@ static int find_cifs_entry(const int xid, struct cifs_tcon *pTcon,
cFYI(1, "calling findnext2"); cFYI(1, "calling findnext2");
rc = CIFSFindNext(xid, pTcon, cifsFile->netfid, rc = CIFSFindNext(xid, pTcon, cifsFile->netfid,
&cifsFile->srch_inf); &cifsFile->srch_inf);
cifs_save_resume_key(cifsFile->srch_inf.last_entry, cifsFile); /* FindFirst/Next set last_entry to NULL on malformed reply */
if (cifsFile->srch_inf.last_entry)
cifs_save_resume_key(cifsFile->srch_inf.last_entry,
cifsFile);
if (rc) if (rc)
return -ENOENT; return -ENOENT;
} }