Re: [Patch v3 2/6] cifs: Allocate validate negotiation request through kmalloc
From: Tom Talpey
Date: Wed Apr 18 2018 - 07:39:55 EST
Two comments.
On 4/17/2018 8:33 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>
The data buffer allocated on the stack can't be DMA'ed, and hence can't send
through RDMA via SMB Direct.
This comment is confusing. Any registered memory can be DMA'd, need to
state the reason for the choice here more clearly.
Fix this by allocating the request on the heap in smb3_validate_negotiate.
Changes in v2:
Removed duplicated code on freeing buffers on function exit.
(Thanks to Parav Pandit <parav@xxxxxxxxxxxx>)
Fixed typo in the patch title.
Changes in v3:
Added "Fixes" to the patch.
Changed sizeof() to use *pointer in place of struct.
Fixes: ff1c038addc4 ("Check SMB3 dialects against downgrade attacks")
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
fs/cifs/smb2pdu.c | 59 ++++++++++++++++++++++++++++++-------------------------
1 file changed, 32 insertions(+), 27 deletions(-)
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 0f044c4..5582a02 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -729,8 +729,8 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
{
- int rc = 0;
- struct validate_negotiate_info_req vneg_inbuf;
+ int ret, rc = -EIO;
+ struct validate_negotiate_info_req *pneg_inbuf;
struct validate_negotiate_info_rsp *pneg_rsp = NULL;
u32 rsplen;
u32 inbuflen; /* max of 4 dialects */
@@ -741,6 +741,9 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
if (tcon->ses->server->rdma)
return 0;
#endif
+ pneg_inbuf = kmalloc(sizeof(*pneg_inbuf), GFP_KERNEL);
+ if (!pneg_inbuf)
+ return -ENOMEM;
Why is this a nonblocking allocation? It would seem more robust to
use GFP_NOFS here.
Tom.
/* In SMB3.11 preauth integrity supersedes validate negotiate */
if (tcon->ses->server->dialect == SMB311_PROT_ID)
@@ -764,63 +767,63 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_NULL)
cifs_dbg(VFS, "Unexpected null user (anonymous) auth flag sent by server\n");
- vneg_inbuf.Capabilities =
+ pneg_inbuf->Capabilities =
cpu_to_le32(tcon->ses->server->vals->req_capabilities);
- memcpy(vneg_inbuf.Guid, tcon->ses->server->client_guid,
+ memcpy(pneg_inbuf->Guid, tcon->ses->server->client_guid,
SMB2_CLIENT_GUID_SIZE);
if (tcon->ses->sign)
- vneg_inbuf.SecurityMode =
+ pneg_inbuf->SecurityMode =
cpu_to_le16(SMB2_NEGOTIATE_SIGNING_REQUIRED);
else if (global_secflags & CIFSSEC_MAY_SIGN)
- vneg_inbuf.SecurityMode =
+ pneg_inbuf->SecurityMode =
cpu_to_le16(SMB2_NEGOTIATE_SIGNING_ENABLED);
else
- vneg_inbuf.SecurityMode = 0;
+ pneg_inbuf->SecurityMode = 0;
if (strcmp(tcon->ses->server->vals->version_string,
SMB3ANY_VERSION_STRING) == 0) {
- vneg_inbuf.Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
- vneg_inbuf.Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
- vneg_inbuf.DialectCount = cpu_to_le16(2);
+ pneg_inbuf->Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
+ pneg_inbuf->Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
+ pneg_inbuf->DialectCount = cpu_to_le16(2);
/* structure is big enough for 3 dialects, sending only 2 */
inbuflen = sizeof(struct validate_negotiate_info_req) - 2;
} else if (strcmp(tcon->ses->server->vals->version_string,
SMBDEFAULT_VERSION_STRING) == 0) {
- vneg_inbuf.Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
- vneg_inbuf.Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
- vneg_inbuf.Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
- vneg_inbuf.DialectCount = cpu_to_le16(3);
+ pneg_inbuf->Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
+ pneg_inbuf->Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
+ pneg_inbuf->Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
+ pneg_inbuf->DialectCount = cpu_to_le16(3);
/* structure is big enough for 3 dialects */
inbuflen = sizeof(struct validate_negotiate_info_req);
} else {
/* otherwise specific dialect was requested */
- vneg_inbuf.Dialects[0] =
+ pneg_inbuf->Dialects[0] =
cpu_to_le16(tcon->ses->server->vals->protocol_id);
- vneg_inbuf.DialectCount = cpu_to_le16(1);
+ pneg_inbuf->DialectCount = cpu_to_le16(1);
/* structure is big enough for 3 dialects, sending only 1 */
inbuflen = sizeof(struct validate_negotiate_info_req) - 4;
}
- rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
+ ret = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
FSCTL_VALIDATE_NEGOTIATE_INFO, true /* is_fsctl */,
- (char *)&vneg_inbuf, sizeof(struct validate_negotiate_info_req),
+ (char *)pneg_inbuf, sizeof(*pneg_inbuf),
(char **)&pneg_rsp, &rsplen);
- if (rc != 0) {
- cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
- return -EIO;
+ if (ret) {
+ cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", ret);
+ goto out_free_inbuf;
}
- if (rsplen != sizeof(struct validate_negotiate_info_rsp)) {
+ if (rsplen != sizeof(*pneg_rsp)) {
cifs_dbg(VFS, "invalid protocol negotiate response size: %d\n",
rsplen);
/* relax check since Mac returns max bufsize allowed on ioctl */
if ((rsplen > CIFSMaxBufSize)
|| (rsplen < sizeof(struct validate_negotiate_info_rsp)))
- goto err_rsp_free;
+ goto out_free_rsp;
}
/* check validate negotiate info response matches what we got earlier */
@@ -838,14 +841,16 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
/* validate negotiate successful */
cifs_dbg(FYI, "validate negotiate info successful\n");
- kfree(pneg_rsp);
- return 0;
+ rc = 0;
+ goto out_free_rsp;
vneg_out:
cifs_dbg(VFS, "protocol revalidation - security settings mismatch\n");
-err_rsp_free:
+out_free_rsp:
kfree(pneg_rsp);
- return -EIO;
+out_free_inbuf:
+ kfree(pneg_inbuf);
+ return rc;
}
enum securityEnum