5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paulo Alcantara <pc@xxxxxxxxxxxxx>
[ Upstream commit 90d025c2e953c11974e76637977c473200593a46 ]
If server replied SMB2_NEGOTIATE with a zero SecurityBufferOffset,
smb2_get_data_area() sets @len to non-zero but return NULL, so
decode_negTokeninit() ends up being called with a NULL @security_blob:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 2 PID: 871 Comm: mount.cifs Not tainted 6.7.0-rc4 #2
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
RIP: 0010:asn1_ber_decoder+0x173/0xc80
Code: 01 4c 39 2c 24 75 09 45 84 c9 0f 85 2f 03 00 00 48 8b 14 24 4c 29 ea 48 83 fa 01 0f 86 1e 07 00 00 48 8b 74 24 28 4d 8d 5d 01 <42> 0f b6 3c 2e 89 fa 40 88 7c 24 5c f7 d2 83 e2 1f 0f 84 3d 07 00
RSP: 0018:ffffc9000063f950 EFLAGS: 00010202
RAX: 0000000000000002 RBX: 0000000000000000 RCX: 000000000000004a
RDX: 000000000000004a RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 000000000000004d R15: 0000000000000000
FS: 00007fce52b0fbc0(0000) GS:ffff88806ba00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001ae64000 CR4: 0000000000750ef0
PKRU: 55555554
Call Trace:
<TASK>
? __die+0x23/0x70
? page_fault_oops+0x181/0x480
? __stack_depot_save+0x1e6/0x480
? exc_page_fault+0x6f/0x1c0
? asm_exc_page_fault+0x26/0x30
? asn1_ber_decoder+0x173/0xc80
? check_object+0x40/0x340
decode_negTokenInit+0x1e/0x30 [cifs]
SMB2_negotiate+0xc99/0x17c0 [cifs]
? smb2_negotiate+0x46/0x60 [cifs]
? srso_alias_return_thunk+0x5/0xfbef5
smb2_negotiate+0x46/0x60 [cifs]
cifs_negotiate_protocol+0xae/0x130 [cifs]
cifs_get_smb_ses+0x517/0x1040 [cifs]
? srso_alias_return_thunk+0x5/0xfbef5
? srso_alias_return_thunk+0x5/0xfbef5
? queue_delayed_work_on+0x5d/0x90
cifs_mount_get_session+0x78/0x200 [cifs]
dfs_mount_share+0x13a/0x9f0 [cifs]
? srso_alias_return_thunk+0x5/0xfbef5
? lock_acquire+0xbf/0x2b0
? find_nls+0x16/0x80
? srso_alias_return_thunk+0x5/0xfbef5
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: 0033:0x7fce52c2ab1e
Fix this by setting @len to zero when @off == 0 so callers won't
attempt to dereference non-existing data areas.
Reported-by: Robert Morris <rtm@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/cifs/smb2misc.c | 26 ++++++++++----------------
1 file changed, 10 insertions(+), 16 deletions(-)
diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index be3df90bb2bcc..b98bba887f84b 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -305,6 +305,9 @@ static const bool has_smb2_data_area[NUMBER_OF_SMB2_COMMANDS] = {
char *
smb2_get_data_area_len(int *off, int *len, struct smb2_sync_hdr *shdr)
{
+ const int max_off = 4096;
+ const int max_len = 128 * 1024;
+
*off = 0;
*len = 0;
@@ -376,29 +379,20 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_sync_hdr *shdr)
* Invalid length or offset probably means data area is invalid, but
* we have little choice but to ignore the data area in this case.
*/
- if (*off > 4096) {
- cifs_dbg(VFS, "offset %d too large, data area ignored\n", *off);
- *len = 0;
- *off = 0;
- } else if (*off < 0) {
- cifs_dbg(VFS, "negative offset %d to data invalid ignore data area\n",
- *off);
+ if (unlikely(*off < 0 || *off > max_off ||
+ *len < 0 || *len > max_len)) {
+ cifs_dbg(VFS, "%s: invalid data area (off=%d len=%d)\n",
+ __func__, *off, *len);
*off = 0;
*len = 0;
- } else if (*len < 0) {
- cifs_dbg(VFS, "negative data length %d invalid, data area ignored\n",
- *len);
- *len = 0;
- } else if (*len > 128 * 1024) {
- cifs_dbg(VFS, "data area larger than 128K: %d\n", *len);
+ } else if (*off == 0) {
*len = 0;
}
/* return pointer to beginning of data area, ie offset from SMB start */
- if ((*off != 0) && (*len != 0))
+ if (*off > 0 && *len > 0)
return (char *)shdr + *off;
- else
- return NULL;
+ return NULL;
}
/*
--
2.43.0
