[PATCH 5.19 0110/1157] ksmbd: prevent out of bound read for SMB2_WRITE

Greg Kroah-Hartman
2022-08-15T22:21:47Z

From: Hyunchul Lee <hyc.lee@gmail.com>

commit ac60778b87e45576d7bfdbd6f53df902654e6f09 upstream.

OOB read memory can be written to a file,
if DataOffset is 0 and Length is too large
in SMB2_WRITE request of compound request.

To prevent this, when checking the length of
the data area of SMB2_WRITE in smb2_get_data_area_len(),
let the minimum of DataOffset be the size of
SMB2 header + the size of SMB2_WRITE header.

This bug can lead an oops looking something like:

[ 798.008715] BUG: KASAN: slab-out-of-bounds in copy_page_from_iter_atomic+0xd3d/0x14b0
[ 798.008724] Read of size 252 at addr ffff88800f863e90 by task kworker/0:2/2859
...
[ 798.008754] Call Trace:
[ 798.008756] <TASK>
[ 798.008759] dump_stack_lvl+0x49/0x5f
[ 798.008764] print_report.cold+0x5e/0x5cf
[ 798.008768] ? __filemap_get_folio+0x285/0x6d0
[ 798.008774] ? copy_page_from_iter_atomic+0xd3d/0x14b0
[ 798.008777] kasan_report+0xaa/0x120
[ 798.008781] ? copy_page_from_iter_atomic+0xd3d/0x14b0
[ 798.008784] kasan_check_range+0x100/0x1e0
[ 798.008788] memcpy+0x24/0x60
[ 798.008792] copy_page_from_iter_atomic+0xd3d/0x14b0
[ 798.008795] ? pagecache_get_page+0x53/0x160
[ 798.008799] ? iov_iter_get_pages_alloc+0x1590/0x1590
[ 798.008803] ? ext4_write_begin+0xfc0/0xfc0
[ 798.008807] ? current_time+0x72/0x210
[ 798.008811] generic_perform_write+0x2c8/0x530
[ 798.008816] ? filemap_fdatawrite_wbc+0x180/0x180
[ 798.008820] ? down_write+0xb4/0x120
[ 798.008824] ? down_write_killable+0x130/0x130
[ 798.008829] ext4_buffered_write_iter+0x137/0x2c0
[ 798.008833] ext4_file_write_iter+0x40b/0x1490
[ 798.008837] ? __fsnotify_parent+0x275/0xb20
[ 798.008842] ? __fsnotify_update_child_dentry_flags+0x2c0/0x2c0
[ 798.008846] ? ext4_buffered_write_iter+0x2c0/0x2c0
[ 798.008851] __kernel_write+0x3a1/0xa70
[ 798.008855] ? __x64_sys_preadv2+0x160/0x160
[ 798.008860] ? security_file_permission+0x4a/0xa0
[ 798.008865] kernel_write+0xbb/0x360
[ 798.008869] ksmbd_vfs_write+0x27e/0xb90 [ksmbd]
[ 798.008881] ? ksmbd_vfs_read+0x830/0x830 [ksmbd]
[ 798.008892] ? _raw_read_unlock+0x2a/0x50
[ 798.008896] smb2_write+0xb45/0x14e0 [ksmbd]
[ 798.008909] ? __kasan_check_write+0x14/0x20
[ 798.008912] ? _raw_spin_lock_bh+0xd0/0xe0
[ 798.008916] ? smb2_read+0x15e0/0x15e0 [ksmbd]
[ 798.008927] ? memcpy+0x4e/0x60
[ 798.008931] ? _raw_spin_unlock+0x19/0x30
[ 798.008934] ? ksmbd_smb2_check_message+0x16af/0x2350 [ksmbd]
[ 798.008946] ? _raw_spin_lock_bh+0xe0/0xe0
[ 798.008950] handle_ksmbd_work+0x30e/0x1020 [ksmbd]
[ 798.008962] process_one_work+0x778/0x11c0
[ 798.008966] ? _raw_spin_lock_irq+0x8e/0xe0
[ 798.008970] worker_thread+0x544/0x1180
[ 798.008973] ? __cpuidle_text_end+0x4/0x4
[ 798.008977] kthread+0x282/0x320
[ 798.008982] ? process_one_work+0x11c0/0x11c0
[ 798.008985] ? kthread_complete_and_exit+0x30/0x30
[ 798.008989] ret_from_fork+0x1f/0x30
[ 798.008995] </TASK>

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-17817
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ksmbd/smb2misc.c | 7 +++++--
fs/ksmbd/smb2pdu.c | 8 +++-----
2 files changed, 8 insertions(+), 7 deletions(-)

--- a/fs/ksmbd/smb2misc.c
+++ b/fs/ksmbd/smb2misc.c
@@ -131,8 +131,11 @@ static int smb2_get_data_area_len(unsign
*len = le16_to_cpu(((struct smb2_read_req *)hdr)->ReadChannelInfoLength);
break;
case SMB2_WRITE:
- if (((struct smb2_write_req *)hdr)->DataOffset) {
- *off = le16_to_cpu(((struct smb2_write_req *)hdr)->DataOffset);
+ if (((struct smb2_write_req *)hdr)->DataOffset ||
+ ((struct smb2_write_req *)hdr)->Length) {
+ *off = max_t(unsigned int,
+ le16_to_cpu(((struct smb2_write_req *)hdr)->DataOffset),
+ offsetof(struct smb2_write_req, Buffer));
*len = le32_to_cpu(((struct smb2_write_req *)hdr)->Length);
break;
}
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -6499,14 +6499,12 @@ int smb2_write(struct ksmbd_work *work)
writethrough = true;

if (is_rdma_channel == false) {
- if ((u64)le16_to_cpu(req->DataOffset) + length >
- get_rfc1002_len(work->request_buf)) {
- pr_err("invalid write data offset %u, smb_len %u\n",
- le16_to_cpu(req->DataOffset),
- get_rfc1002_len(work->request_buf));
+ if (le16_to_cpu(req->DataOffset) <
+ offsetof(struct smb2_write_req, Buffer)) {
err = -EINVAL;
goto out;
}
+
data_buf = (char *)(((char *)&req->hdr.ProtocolId) +
le16_to_cpu(req->DataOffset));