staging: rtl8723bs: fix protected RX frame validation in decrypt path
PATCH v3 1/1 staging: rtl8723bs: fix protected RX frame validation in decrypt path
From: Tianchu Chen <[email protected]>
The RX software decrypt path mishandles crafted protected frames from a malicious AP in two ways:
1) decryptor() never checks that a protected frame is long enough to hold the 802.11 header plus the per-cipher trailer. All of rtw_wep_decrypt(), rtw_tkip_decrypt() and rtw_aes_decrypt() compute
length = hdr.len - hdrlen - iv_len;
and act on the result, and recvframe_chkmic() similarly computes
datalen = hdr.len - hdrlen - iv_len - icv_len - 8;
for TKIP (the 8-byte Michael MIC is not accounted for in icv_len). A frame shorter than hdrlen + iv_len + icv_len (+ 8 for TKIP) underflows these unsigned subtractions, turning into a ~4 GiB iteration count in aes_decipher()/arc4_crypt()/rtw_seccalctkipmic() or a ~4 GiB crc32_le() length, causing out-of-bounds reads/writes of up to ~4 GiB starting from the rx skb. Reject such frames in decryptor() before touching the IV; this covers all three ciphers and the TKIP MIC check, and also keeps the unconditional iv[3] access within the frame.
2) validate_80211w_mgmt() keeps using the frame - two memcpys through the stale rx_data pointer and a pkt_len update - before checking whether decryptor() returned NULL. On decrypt failure (e.g. a unicast protected deauth/disassoc/action frame with a bad MIC, which this path always software-decrypts) the skb has already been freed, so this is a use-after-free read/write, and the caller's error path frees the frame a second time, drifting free_recvframe_cnt. Bail out immediately when decryptor() fails, freeing the temporary mgmt_DATA buffer first.
Discovered by Atuin - Automated Vulnerability Discovery Engine.
---
v3: improve formatting.
v2: no code change; adds the real-hardware test report requested for LLM-assisted staging patches.
Test report
=========================
Victim: Wintel CX-W8 mini PC (Atom Z3735F, on-board RTL8723BS chip, staging r8723bs,
Debian 13.6.0/Kernel 6.12.94), bought from the second-hand market for this test.
Attacker: ESP32-S3 dev board running custom firmware as a rogue AP. Patching a proprietary
library is needed. Details available to reviewers upon request.
The decryptor bug is reachable at the association stage: the vulnerable decrypt path is taken before any key is installed, so the attacker never needs to pass key verification - the rogue AP's PSK does not need to match the victim's. Knowing an SSID the victim will auto-join is enough.
Once the victim associates, the rogue AP send 802.11 data frames with FromDS + Protected bit set and a total length of 24..31 bytes, i.e. shorter than their own CCMP IV (hdrlen 24 + iv_len 8). With no key in the HW CAM the frames reach decryptor() with bdecrypted == 0, and rtw_aes_decrypt() computes length = (24..31) - 24 - 8, a ~4 GiB underflow fed straight into aes_decipher().
Result: the victim kernel panics within seconds of association. Captured via netconsole:
[ 939.937797] Oops: general protection fault, probably for non-canonical address 0x6de15a87d1c57856: 0000 [#1] PREEMPT SMP PTI [ 939.938075] CPU: 3 UID: 0 PID: 1637 Comm: Xorg Tainted: G C 6.12.94+deb13-amd64 #1 Debian 6.12.94-1 [ 939.938288] Tainted: [C]=CRAP [ 939.938368] Hardware name: Insyde Intel CX-W8/Intel CX-W8, BIOS M.W8RAAA01 04/17/2015 [ 939.938515] RIP: 0010:i915_gem_do_execbuffer+0xbd1/0x2950 [i915] [ 939.939945] Code: e2 fe 48 89 50 20 48 8d 74 24 58 4c 89 e9 48 8d 7c 24 60 44 89 f2 e8 ce c2 ff ff 85 c0 0f 85 9d 03 00 00 49 8b bd b8 00 00 00 <48> 83 bf 50 04 00 00 00 74 31 e8 10 1b 01 00 85 c0 0f 85 91 18 00 [ 939.940255] RSP: 0018:ffffccdfc0b17788 EFLAGS: 00010246 [ 939.940382] RAX: 0000000000000000 RBX: 0000000000000009 RCX: 00000000fffffff5 [ 939.940524] RDX: 0000000000000001 RSI: ffff8c5aa8d4d800 RDI: 6de15a87d1c57406 [ 939.940664] RBP: 00000000000001f8 R08: ffff8c5aa92e4a90 R09: ffff8c5aaa953518 [ 939.940805] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000003a9 [ 939.940942] R13: ffff8c5af99f1680 R14: 0000000000000009 R15: 0000000000000000 [ 939.941081] FS: 00007f3856594b00(0000) GS:ffff8c5afb980000(0000) knlGS:0000000000000000 [ 939.941238] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 939.941358] CR2: 00007f3856155770 CR3: 000000002b7e6000 CR4: 00000000001026f0 [ 939.941500] Call Trace: [ 939.941579] <TASK> [ 939.941702] i915_gem_execbuffer2_ioctl+0x13b/0x260 [i915] [ 939.943134] ? __pfx_i915_gem_execbuffer2_ioctl+0x10/0x10 [i915] [ 939.944543] drm_ioctl_kernel+0xb0/0x100 [drm] [ 939.945069] drm_ioctl+0x277/0x4d0 [drm] [ 939.945571] ? __pfx_i915_gem_execbuffer2_ioctl+0x10/0x10 [i915] [ 939.946997] __x64_sys_ioctl+0x97/0xc0 [ 939.947119] do_syscall_64+0x87/0x1b0 [ 939.947235] ? timerqueue_del+0x2e/0x50 [ 939.947343] ? tomoyo_init_request_info+0x99/0xc0 [ 939.947470] ? tomoyo_path_number_perm+0x8c/0x1f0 [ 939.947589] ? ww_mutex_lock_interruptible+0x18/0x80 [ 939.947725] ? i915_gem_madvise_ioctl+0x239/0x340 [i915] [ 939.949150] ? __pfx_i915_gem_madvise_ioctl+0x10/0x10 [i915] [ 939.950571] ? drm_ioctl_kernel+0xb0/0x100 [drm] [ 939.951086] ? __check_object_size+0x50/0x210 [ 939.955215] ? _copy_to_user+0x36/0x50 [ 939.959506] ? drm_ioctl+0x2a1/0x4d0 [drm] [ 939.964159] ? __pfx_i915_gem_madvise_ioctl+0x10/0x10 [i915] [ 939.969804] ? arch_exit_to_user_mode_prepare.isra.0+0x16/0xa0 [ 939.974146] ? syscall_exit_to_user_mode+0x37/0x1b0 [ 939.978488] ? do_syscall_64+0x93/0x1b0 [ 939.982872] ? arch_exit_to_user_mode_prepare.isra.0+0x16/0xa0 [ 939.987300] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 939.991768] RIP: 0033:0x7f385691491b [ 939.996285] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00 [ 940.001138] RSP: 002b:00007ffdb0cf6710 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 940.006061] RAX: ffffffffffffffda RBX: 0000564e32defb08 RCX: 00007f385691491b [ 940.011048] RDX: 00007ffdb0cf6790 RSI: 0000000040406469 RDI: 0000000000000013 [ 940.016090] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000004 [ 940.021150] R10: 0000000000000020 R11: 0000000000000246 R12: 00007ffdb0cf6790 [ 940.026256] R13: 0000564e32dc3a50 R14: 00000000000000dc R15: 0000000000000013 [ 940.031431] </TASK>
The oops surfacing in i915 rather than in the driver is expected:
A non-canonical garbage pointer in an unrelated subsystem is the expected signature of the multi-GB linear decipher starting from the rx skb.
drivers/staging/rtl8723bs/core/rtw_recv.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
drivers/staging/rtl8723bs/core/rtw_recv.c +18 -3
@@ -426,8 +426,21 @@ static union recv_frame *decryptor(struct adapter *padapter, union recv_frame *pu32 res = _SUCCESS;if (prxattrib->encrypt >0 ) { -u8 *iv = precv_frame->u.hdr.rx_data + prxattrib->hdrlen; +u8 *iv; +u32 min_len = prxattrib->hdrlen + prxattrib->iv_len + prxattrib->icv_len; +/* TKIP appends an 8-byte Michael MIC that icv_len doesn't account for */ +if (prxattrib->encrypt == _TKIP_) + min_len +=8 ; + +/* a protected frame must be long enough to hold the IV and ICV/MIC */ +if (precv_frame->u.hdr.len < min_len) { +rtw_free_recvframe (precv_frame, + &padapter->recvpriv.free_recv_queue); +return NULL ; + } + + iv = precv_frame->u.hdr.rx_data + prxattrib->hdrlen; prxattrib->key_index = (((iv[3 ]) >>6 ) &0x3 );if (prxattrib->key_index >WEP_KEYS ) {
@@ -1395,6 +1408,10 @@ static signed int validate_80211w_mgmt(struct adapter *adapter, union recv_frameif (!mgmt_DATA) goto validate_80211w_fail; precv_frame =decryptor (adapter, precv_frame); +if (!precv_frame) { +kfree (mgmt_DATA); + goto validate_80211w_fail; + }/* save actual management data frame body */ memcpy (mgmt_DATA, ptr + pattrib->hdrlen + pattrib->iv_len, data_len);/* overwrite the iv field */
@@ -1402,8 +1419,6 @@ static signed int validate_80211w_mgmt(struct adapter *adapter, union recv_frame/* remove the iv and icv length */ pattrib->pkt_len = pattrib->pkt_len - pattrib->iv_len - pattrib->icv_len;kfree (mgmt_DATA); -if (!precv_frame) - goto validate_80211w_fail; }else if (is_multicast_ether_addr (GetAddr1Ptr (ptr)) && (subtype ==WIFI_DEAUTH || subtype ==WIFI_DISASSOC )) {signed int BIP_ret = _SUCCESS;
Signature · 1 line
2.51.0