soreceive_stream: mbuf leak if called with mp0 and MSG_WAITALL
Mikolaj Golub
trociny at freebsd.org
Thu Mar 8 11:15:39 UTC 2012
Hi,
On Tue, 06 Mar 2012 20:50:34 +0100 Andre Oppermann wrote:
AO> On 05.09.2011 21:58, Mikolaj Golub wrote:
>>
>> On Sun, 04 Sep 2011 12:30:53 +0300 Mikolaj Golub wrote:
>>
>> MG> Apparently soreceive_stream() has an issue if it is called to receive data as a
>> MG> mbuf chain (by supplying an non zero mbuf **mp0) and with MSG_WAITALL set.
>>
>> MG> I ran into this issue with smbfs, which uses soreceive() exactly in this way
>> MG> (see netsmb/smb_trantcp.c:nbssn_recv()).
>>
>> Stressing smbfs a little I also observed the following soreceive_stream()
>> related panic:
AO> Hi Mikolaj,
AO> thank you very much for testing, reporting and fixing bugs in soreceive_stream().
AO> I've altered your proposed patches a bit and committed them into my workqueue
AO> with the following revisions:
AO> http://svn.freebsd.org/changeset/base/232617
AO> http://svn.freebsd.org/changeset/base/232618
AO> Would you mind testing them again before they go into HEAD?
With this patch smb mount fails with the error:
smb_iod_recvall: tran return NULL without error
AO> Index: sys/kern/uipc_socket.c
AO> ===================================================================
AO> --- sys/kern/uipc_socket.c (revision 232616)
AO> +++ sys/kern/uipc_socket.c (revision 232617)
AO> @@ -2044,7 +2044,7 @@ deliver:
AO> if (mp0 != NULL) {
AO> /* Dequeue as many mbufs as possible. */
AO> if (!(flags & MSG_PEEK) && len >= sb->sb_mb->m_len) {
AO> - for (*mp0 = m = sb->sb_mb;
AO> + for (m = sb->sb_mb;
AO> m != NULL && m->m_len <= len;
AO> m = m->m_next) {
AO> len -= m->m_len;
AO> @@ -2052,10 +2052,15 @@ deliver:
AO> sbfree(sb, m);
AO> n = m;
AO> }
AO> + n->m_next = NULL;
AO> sb->sb_mb = m;
AO> + sb->sb_lastrecord = sb->sb_mb;
AO> if (sb->sb_mb == NULL)
AO> SB_EMPTY_FIXUP(sb);
AO> - n->m_next = NULL;
AO> + if (*mp0 != NULL)
AO> + m_cat(*mp0, m);
AO> + else
AO> + *mp0 = m;
AO> }
At that moment m points to the end of the chain. Shouldn't *mp0 be set to
sb->sb_mb before the "for" loop?
AO> /* Copy the remainder. */
AO> if (len > 0) {
AO> @@ -2066,9 +2071,9 @@ deliver:
AO> if (m == NULL)
AO> len = 0; /* Don't flush data from sockbuf. */
AO> else
AO> - uio->uio_resid -= m->m_len;
AO> + uio->uio_resid -= len;
AO> if (*mp0 != NULL)
AO> - n->m_next = m;
AO> + m_cat(*mp0, m);
AO> else
AO> *mp0 = m;
AO> if (*mp0 == NULL) {
AO>
--
Mikolaj Golub
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