[PATCH 5.10 005/122] smb: client: fix potential OOBs in smb2_parse_contexts()

Greg Kroah-Hartman
2024-02-27T14:26:02Z

From: Paulo Alcantara <pc@manguebit.com>

[ Upstream commit af1689a9b7701d9907dfc84d2a4b57c4bc907144 ]

Validate offsets and lengths before dereferencing create contexts in
smb2_parse_contexts().

This fixes following oops when accessing invalid create contexts from
server:

BUG: unable to handle page fault for address: ffff8881178d8cc3
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 4a01067 P4D 4a01067 PUD 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 1736 Comm: mount.cifs Not tainted 6.7.0-rc4 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
RIP: 0010:smb2_parse_contexts+0xa0/0x3a0 [cifs]
Code: f8 10 75 13 48 b8 93 ad 25 50 9c b4 11 e7 49 39 06 0f 84 d2 00
00 00 8b 45 00 85 c0 74 61 41 29 c5 48 01 c5 41 83 fd 0f 76 55 <0f> b7
7d 04 0f b7 45 06 4c 8d 74 3d 00 66 83 f8 04 75 bc ba 04 00
RSP: 0018:ffffc900007939e0 EFLAGS: 00010216
RAX: ffffc90000793c78 RBX: ffff8880180cc000 RCX: ffffc90000793c90
RDX: ffffc90000793cc0 RSI: ffff8880178d8cc0 RDI: ffff8880180cc000
RBP: ffff8881178d8cbf R08: ffffc90000793c22 R09: 0000000000000000
R10: ffff8880180cc000 R11: 0000000000000024 R12: 0000000000000000
R13: 0000000000000020 R14: 0000000000000000 R15: ffffc90000793c22
FS: 00007f873753cbc0(0000) GS:ffff88806bc00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8881178d8cc3 CR3: 00000000181ca000 CR4: 0000000000750ef0
PKRU: 55555554
Call Trace:
<TASK>
? __die+0x23/0x70
? page_fault_oops+0x181/0x480
? search_module_extables+0x19/0x60
? srso_alias_return_thunk+0x5/0xfbef5
? exc_page_fault+0x1b6/0x1c0
? asm_exc_page_fault+0x26/0x30
? smb2_parse_contexts+0xa0/0x3a0 [cifs]
SMB2_open+0x38d/0x5f0 [cifs]
? smb2_is_path_accessible+0x138/0x260 [cifs]
smb2_is_path_accessible+0x138/0x260 [cifs]
cifs_is_path_remote+0x8d/0x230 [cifs]
cifs_mount+0x7e/0x350 [cifs]
cifs_smb3_do_mount+0x128/0x780 [cifs]
smb3_get_tree+0xd9/0x290 [cifs]
vfs_get_tree+0x2c/0x100
? capable+0x37/0x70
path_mount+0x2d7/0xb80
? srso_alias_return_thunk+0x5/0xfbef5
? _raw_spin_unlock_irqrestore+0x44/0x60
__x64_sys_mount+0x11a/0x150
do_syscall_64+0x47/0xf0
entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f8737657b1e

Reported-by: Robert Morris <rtm@csail.mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
[Guru: Removed changes to cached_dir.c and checking return value
of smb2_parse_contexts in smb2ops.c]
Signed-off-by: Guruswamy Basavaiah <guruswamy.basavaiah@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/smb2ops.c | 4 +-
fs/cifs/smb2pdu.c | 91 +++++++++++++++++++++++++++++++---------------------
fs/cifs/smb2proto.h | 12 ++++--
3 files changed, 65 insertions(+), 42 deletions(-)

--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -818,10 +818,12 @@ int open_shroot(unsigned int xid, struct
if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE) {
kref_get(&tcon->crfid.refcount);
tcon->crfid.has_lease = true;
- smb2_parse_contexts(server, o_rsp,
+ rc = smb2_parse_contexts(server, rsp_iov,
&oparms.fid->epoch,
oparms.fid->lease_key, &oplock,
NULL, NULL);
+ if (rc)
+ goto oshr_exit;
} else
goto oshr_exit;

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1991,17 +1991,18 @@ parse_posix_ctxt(struct create_context *
posix->nlink, posix->mode, posix->reparse_tag);
}

-void
-smb2_parse_contexts(struct TCP_Server_Info *server,
- struct smb2_create_rsp *rsp,
- unsigned int *epoch, char *lease_key, __u8 *oplock,
- struct smb2_file_all_info *buf,
- struct create_posix_rsp *posix)
+int smb2_parse_contexts(struct TCP_Server_Info *server,
+ struct kvec *rsp_iov,
+ unsigned int *epoch,
+ char *lease_key, __u8 *oplock,
+ struct smb2_file_all_info *buf,
+ struct create_posix_rsp *posix)
{
- char *data_offset;
+ struct smb2_create_rsp *rsp = rsp_iov->iov_base;
struct create_context *cc;
- unsigned int next;
- unsigned int remaining;
+ size_t rem, off, len;
+ size_t doff, dlen;
+ size_t noff, nlen;
char *name;
static const char smb3_create_tag_posix[] = {
0x93, 0xAD, 0x25, 0x50, 0x9C,
@@ -2010,45 +2011,63 @@ smb2_parse_contexts(struct TCP_Server_In
};

*oplock = 0;
- data_offset = (char *)rsp + le32_to_cpu(rsp->CreateContextsOffset);
- remaining = le32_to_cpu(rsp->CreateContextsLength);
- cc = (struct create_context *)data_offset;
+
+ off = le32_to_cpu(rsp->CreateContextsOffset);
+ rem = le32_to_cpu(rsp->CreateContextsLength);
+ if (check_add_overflow(off, rem, &len) || len > rsp_iov->iov_len)
+ return -EINVAL;
+ cc = (struct create_context *)((u8 *)rsp + off);

/* Initialize inode number to 0 in case no valid data in qfid context */
if (buf)
buf->IndexNumber = 0;

- while (remaining >= sizeof(struct create_context)) {
- name = le16_to_cpu(cc->NameOffset) + (char *)cc;
- if (le16_to_cpu(cc->NameLength) == 4 &&
- strncmp(name, SMB2_CREATE_REQUEST_LEASE, 4) == 0)
- *oplock = server->ops->parse_lease_buf(cc, epoch,
- lease_key);
- else if (buf && (le16_to_cpu(cc->NameLength) == 4) &&
- strncmp(name, SMB2_CREATE_QUERY_ON_DISK_ID, 4) == 0)
- parse_query_id_ctxt(cc, buf);
- else if ((le16_to_cpu(cc->NameLength) == 16)) {
- if (posix &&
- memcmp(name, smb3_create_tag_posix, 16) == 0)
+ while (rem >= sizeof(*cc)) {
+ doff = le16_to_cpu(cc->DataOffset);
+ dlen = le32_to_cpu(cc->DataLength);
+ if (check_add_overflow(doff, dlen, &len) || len > rem)
+ return -EINVAL;
+
+ noff = le16_to_cpu(cc->NameOffset);
+ nlen = le16_to_cpu(cc->NameLength);
+ if (noff + nlen >= doff)
+ return -EINVAL;
+
+ name = (char *)cc + noff;
+ switch (nlen) {
+ case 4:
+ if (!strncmp(name, SMB2_CREATE_REQUEST_LEASE, 4)) {
+ *oplock = server->ops->parse_lease_buf(cc, epoch,
+ lease_key);
+ } else if (buf &&
+ !strncmp(name, SMB2_CREATE_QUERY_ON_DISK_ID, 4)) {
+ parse_query_id_ctxt(cc, buf);
+ }
+ break;
+ case 16:
+ if (posix && !memcmp(name, smb3_create_tag_posix, 16))
parse_posix_ctxt(cc, buf, posix);
+ break;
+ default:
+ cifs_dbg(FYI, "%s: unhandled context (nlen=%zu dlen=%zu)\n",
+ __func__, nlen, dlen);
+ if (IS_ENABLED(CONFIG_CIFS_DEBUG2))
+ cifs_dump_mem("context data: ", cc, dlen);
+ break;
}
- /* else {
- cifs_dbg(FYI, "Context not matched with len %d\n",
- le16_to_cpu(cc->NameLength));
- cifs_dump_mem("Cctxt name: ", name, 4);
- } */

- next = le32_to_cpu(cc->Next);
- if (!next)
+ off = le32_to_cpu(cc->Next);
+ if (!off)
break;
- remaining -= next;
- cc = (struct create_context *)((char *)cc + next);
+ if (check_sub_overflow(rem, off, &rem))
+ return -EINVAL;
+ cc = (struct create_context *)((u8 *)cc + off);
}

if (rsp->OplockLevel != SMB2_OPLOCK_LEVEL_LEASE)
*oplock = rsp->OplockLevel;

- return;
+ return 0;
}

static int
@@ -2915,8 +2934,8 @@ SMB2_open(const unsigned int xid, struct
}

- smb2_parse_contexts(server, rsp, &oparms->fid->epoch,
- oparms->fid->lease_key, oplock, buf, posix);
+ rc = smb2_parse_contexts(server, &rsp_iov, &oparms->fid->epoch,
+ oparms->fid->lease_key, oplock, buf, posix);
creat_exit:
SMB2_open_free(&rqst);
free_rsp_buf(resp_buftype, rsp);
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -270,11 +270,13 @@ extern int smb3_validate_negotiate(const

extern enum securityEnum smb2_select_sectype(struct TCP_Server_Info *,
enum securityEnum);
-extern void smb2_parse_contexts(struct TCP_Server_Info *server,
- struct smb2_create_rsp *rsp,
- unsigned int *epoch, char *lease_key,
- __u8 *oplock, struct smb2_file_all_info *buf,
- struct create_posix_rsp *posix);
+int smb2_parse_contexts(struct TCP_Server_Info *server,
+ struct kvec *rsp_iov,
+ unsigned int *epoch,
+ char *lease_key, __u8 *oplock,
+ struct smb2_file_all_info *buf,
+ struct create_posix_rsp *posix);
+
extern int smb3_encryption_required(const struct cifs_tcon *tcon);
extern int smb2_validate_iov(unsigned int offset, unsigned int buffer_length,
struct kvec *iov, unsigned int min_buf_size);