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Subject[PATCH 3.8 25/81] CIFS: Fix too big maxBuf size for SMB3 mounts
Date
3.8.13.20 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Shilovsky <piastry@etersoft.ru>

commit 2365c4eaf077c48574ab6f143960048fc0f31518 upstream.

SMB3 servers can respond with MaxTransactSize of more than 4M
that can cause a memory allocation error returned from kmalloc
in a lock codepath. Also the client doesn't support multicredit
requests now and allows buffer sizes of 65536 bytes only. Set
MaxTransactSize to this maximum supported value.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
fs/cifs/smb2glob.h | 3 +++
fs/cifs/smb2ops.c | 14 ++++----------
fs/cifs/smb2pdu.c | 4 +++-
3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/cifs/smb2glob.h b/fs/cifs/smb2glob.h
index 7c0e214..cc592ef 100644
--- a/fs/cifs/smb2glob.h
+++ b/fs/cifs/smb2glob.h
@@ -55,4 +55,7 @@
#define SMB2_NTLMV2_SESSKEY_SIZE (16)
#define SMB2_HMACSHA256_SIZE (32)

+/* Maximum buffer size value we can send with 1 credit */
+#define SMB2_MAX_BUFFER_SIZE 65536
+
#endif /* _SMB2_GLOB_H */
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index bceffe7..542efd2 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -181,11 +181,8 @@ smb2_negotiate_wsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
/* start with specified wsize, or default */
wsize = volume_info->wsize ? volume_info->wsize : CIFS_DEFAULT_IOSIZE;
wsize = min_t(unsigned int, wsize, server->max_write);
- /*
- * limit write size to 2 ** 16, because we don't support multicredit
- * requests now.
- */
- wsize = min_t(unsigned int, wsize, 2 << 15);
+ /* set it to the maximum buffer size value we can send with 1 credit */
+ wsize = min_t(unsigned int, wsize, SMB2_MAX_BUFFER_SIZE);

return wsize;
}
@@ -199,11 +196,8 @@ smb2_negotiate_rsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
/* start with specified rsize, or default */
rsize = volume_info->rsize ? volume_info->rsize : CIFS_DEFAULT_IOSIZE;
rsize = min_t(unsigned int, rsize, server->max_read);
- /*
- * limit write size to 2 ** 16, because we don't support multicredit
- * requests now.
- */
- rsize = min_t(unsigned int, rsize, 2 << 15);
+ /* set it to the maximum buffer size value we can send with 1 credit */
+ rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);

return rsize;
}
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 41d9d07..8a9b5df 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -407,7 +407,9 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
}
server->dialect = le16_to_cpu(rsp->DialectRevision);

- server->maxBuf = le32_to_cpu(rsp->MaxTransactSize);
+ /* set it to the maximum buffer size value we can send with 1 credit */
+ server->maxBuf = min_t(unsigned int, le32_to_cpu(rsp->MaxTransactSize),
+ SMB2_MAX_BUFFER_SIZE);
server->max_read = le32_to_cpu(rsp->MaxReadSize);
server->max_write = le32_to_cpu(rsp->MaxWriteSize);
/* BB Do we need to validate the SecurityMode? */
--
1.8.3.2


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