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Subject[PATCH 4.14 12/53] cifs: Fix slab-out-of-bounds in send_set_info() on SMB2 ACE setting
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Stefano Brivio <sbrivio@redhat.com>

commit f46ecbd97f508e68a7806291a139499794874f3d upstream.

A "small" CIFS buffer is not big enough in general to hold a
setacl request for SMB2, and we end up overflowing the buffer in
send_set_info(). For instance:

# mount.cifs //127.0.0.1/test /mnt/test -o username=test,password=test,nounix,cifsacl
# touch /mnt/test/acltest
# getcifsacl /mnt/test/acltest
REVISION:0x1
CONTROL:0x9004
OWNER:S-1-5-21-2926364953-924364008-418108241-1000
GROUP:S-1-22-2-1001
ACL:S-1-5-21-2926364953-924364008-418108241-1000:ALLOWED/0x0/0x1e01ff
ACL:S-1-22-2-1001:ALLOWED/0x0/R
ACL:S-1-22-2-1001:ALLOWED/0x0/R
ACL:S-1-5-21-2926364953-924364008-418108241-1000:ALLOWED/0x0/0x1e01ff
ACL:S-1-1-0:ALLOWED/0x0/R
# setcifsacl -a "ACL:S-1-22-2-1004:ALLOWED/0x0/R" /mnt/test/acltest

this setacl will cause the following KASAN splat:

[ 330.777927] BUG: KASAN: slab-out-of-bounds in send_set_info+0x4dd/0xc20 [cifs]
[ 330.779696] Write of size 696 at addr ffff88010d5e2860 by task setcifsacl/1012

[ 330.781882] CPU: 1 PID: 1012 Comm: setcifsacl Not tainted 4.18.0-rc2+ #2
[ 330.783140] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 330.784395] Call Trace:
[ 330.784789] dump_stack+0xc2/0x16b
[ 330.786777] print_address_description+0x6a/0x270
[ 330.787520] kasan_report+0x258/0x380
[ 330.788845] memcpy+0x34/0x50
[ 330.789369] send_set_info+0x4dd/0xc20 [cifs]
[ 330.799511] SMB2_set_acl+0x76/0xa0 [cifs]
[ 330.801395] set_smb2_acl+0x7ac/0xf30 [cifs]
[ 330.830888] cifs_xattr_set+0x963/0xe40 [cifs]
[ 330.840367] __vfs_setxattr+0x84/0xb0
[ 330.842060] __vfs_setxattr_noperm+0xe6/0x370
[ 330.843848] vfs_setxattr+0xc2/0xd0
[ 330.845519] setxattr+0x258/0x320
[ 330.859211] path_setxattr+0x15b/0x1b0
[ 330.864392] __x64_sys_setxattr+0xc0/0x160
[ 330.866133] do_syscall_64+0x14e/0x4b0
[ 330.876631] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 330.878503] RIP: 0033:0x7ff2e507db0a
[ 330.880151] Code: 48 8b 0d 89 93 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 bc 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 56 93 2c 00 f7 d8 64 89 01 48
[ 330.885358] RSP: 002b:00007ffdc4903c18 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
[ 330.887733] RAX: ffffffffffffffda RBX: 000055d1170de140 RCX: 00007ff2e507db0a
[ 330.890067] RDX: 000055d1170de7d0 RSI: 000055d115b39184 RDI: 00007ffdc4904818
[ 330.892410] RBP: 0000000000000001 R08: 0000000000000000 R09: 000055d1170de7e4
[ 330.894785] R10: 00000000000002b8 R11: 0000000000000246 R12: 0000000000000007
[ 330.897148] R13: 000055d1170de0c0 R14: 0000000000000008 R15: 000055d1170de550

[ 330.901057] Allocated by task 1012:
[ 330.902888] kasan_kmalloc+0xa0/0xd0
[ 330.904714] kmem_cache_alloc+0xc8/0x1d0
[ 330.906615] mempool_alloc+0x11e/0x380
[ 330.908496] cifs_small_buf_get+0x35/0x60 [cifs]
[ 330.910510] smb2_plain_req_init+0x4a/0xd60 [cifs]
[ 330.912551] send_set_info+0x198/0xc20 [cifs]
[ 330.914535] SMB2_set_acl+0x76/0xa0 [cifs]
[ 330.916465] set_smb2_acl+0x7ac/0xf30 [cifs]
[ 330.918453] cifs_xattr_set+0x963/0xe40 [cifs]
[ 330.920426] __vfs_setxattr+0x84/0xb0
[ 330.922284] __vfs_setxattr_noperm+0xe6/0x370
[ 330.924213] vfs_setxattr+0xc2/0xd0
[ 330.926008] setxattr+0x258/0x320
[ 330.927762] path_setxattr+0x15b/0x1b0
[ 330.929592] __x64_sys_setxattr+0xc0/0x160
[ 330.931459] do_syscall_64+0x14e/0x4b0
[ 330.933314] entry_SYSCALL_64_after_hwframe+0x44/0xa9

[ 330.936843] Freed by task 0:
[ 330.938588] (stack is not available)

[ 330.941886] The buggy address belongs to the object at ffff88010d5e2800
which belongs to the cache cifs_small_rq of size 448
[ 330.946362] The buggy address is located 96 bytes inside of
448-byte region [ffff88010d5e2800, ffff88010d5e29c0)
[ 330.950722] The buggy address belongs to the page:
[ 330.952789] page:ffffea0004357880 count:1 mapcount:0 mapping:ffff880108fdca80 index:0x0 compound_mapcount: 0
[ 330.955665] flags: 0x17ffffc0008100(slab|head)
[ 330.957760] raw: 0017ffffc0008100 dead000000000100 dead000000000200 ffff880108fdca80
[ 330.960356] raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
[ 330.963005] page dumped because: kasan: bad access detected

[ 330.967039] Memory state around the buggy address:
[ 330.969255] ffff88010d5e2880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 330.971833] ffff88010d5e2900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 330.974397] >ffff88010d5e2980: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 330.976956] ^
[ 330.979226] ffff88010d5e2a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 330.981755] ffff88010d5e2a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 330.984225] ==================================================================

Fix this by allocating a regular CIFS buffer in
smb2_plain_req_init() if the request command is SMB2_SET_INFO.

Reported-by: Jianhong Yin <jiyin@redhat.com>
Fixes: 366ed846df60 ("cifs: Use smb 2 - 3 and cifsacl mount options setacl function")
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-and-tested-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/smb2pdu.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -338,7 +338,10 @@ smb2_plain_req_init(__le16 smb2_command,
return rc;

/* BB eventually switch this to SMB2 specific small buf size */
- *request_buf = cifs_small_buf_get();
+ if (smb2_command == SMB2_SET_INFO)
+ *request_buf = cifs_buf_get();
+ else
+ *request_buf = cifs_small_buf_get();
if (*request_buf == NULL) {
/* BB should we add a retry in here if not a writepage? */
return -ENOMEM;
@@ -3168,7 +3171,7 @@ send_set_info(const unsigned int xid, st
}

rc = SendReceive2(xid, ses, iov, num, &resp_buftype, flags, &rsp_iov);
- cifs_small_buf_release(req);
+ cifs_buf_release(req);
rsp = (struct smb2_set_info_rsp *)rsp_iov.iov_base;

if (rc != 0)

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