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brcmfmac: Fix out of bounds memory access during fw load

PATCH In review Lyude Paul 2 participants 3 messages Nov 24, 2018 – Nov 29, 2018

Subsystems (4)
Networking Network drivers Stable branch Broadcom BRCM80211 IEEE802.11 wireless drivers
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Lyude Paul

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PATCH 1/1 brcmfmac: Fix out of bounds memory access during fw load

I ended up tracking down some rather nasty issues with f2fs (and other filesystem modules) constantly crashing on my kernel down to a combination of out of bounds memory accesses, one of which was coming from brcmfmac during module load:

[   30.891382] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4356-sdio for chip BCM4356/2
[   30.894437] ==================================================================
[   30.901581] BUG: KASAN: global-out-of-bounds in brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.909935] Read of size 1 at addr ffff2000024865df by task kworker/6:2/387
[   30.916805]
[   30.918261] CPU: 6 PID: 387 Comm: kworker/6:2 Tainted: G           O      4.20.0-rc3Lyude-Test+ #19
[   30.927251] Hardware name: amlogic khadas-vim2/khadas-vim2, BIOS 2018.07-rc2-armbian 09/11/2018
[   30.935964] Workqueue: events brcmf_driver_register [brcmfmac]
[   30.941641] Call trace:
[   30.944058]  dump_backtrace+0x0/0x3e8
[   30.947676]  show_stack+0x14/0x20
[   30.950968]  dump_stack+0x130/0x1c4
[   30.954406]  print_address_description+0x60/0x25c
[   30.959066]  kasan_report+0x1b4/0x368
[   30.962683]  __asan_report_load1_noabort+0x18/0x20
[   30.967547]  brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.967639]  brcmf_sdio_probe+0x163c/0x2050 [brcmfmac]
[   30.978035]  brcmf_ops_sdio_probe+0x598/0xa08 [brcmfmac]
[   30.983254]  sdio_bus_probe+0x190/0x398
[   30.983270]  really_probe+0x2a0/0xa70
[   30.983296]  driver_probe_device+0x1b4/0x2d8
[   30.994901]  __driver_attach+0x200/0x280
[   30.994914]  bus_for_each_dev+0x10c/0x1a8
[   30.994925]  driver_attach+0x38/0x50
[   30.994935]  bus_add_driver+0x330/0x608
[   30.994953]  driver_register+0x140/0x388
[   31.013965]  sdio_register_driver+0x74/0xa0
[   31.014076]  brcmf_sdio_register+0x14/0x60 [brcmfmac]
[   31.023177]  brcmf_driver_register+0xc/0x18 [brcmfmac]
[   31.023209]  process_one_work+0x654/0x1080
[   31.032266]  worker_thread+0x4f0/0x1308
[   31.032286]  kthread+0x2a8/0x320
[   31.039254]  ret_from_fork+0x10/0x1c
[   31.039269]
[   31.044226] The buggy address belongs to the variable:
[   31.044351]  brcmf_firmware_path+0x11f/0xfffffffffffd3b40 [brcmfmac]
[   31.055601]
[   31.057031] Memory state around the buggy address:
[   31.061800]  ffff200002486480: 04 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
[   31.068983]  ffff200002486500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.068993] >ffff200002486580: 00 00 00 00 00 00 00 00 fa fa fa fa 00 00 00 00
[   31.068999]                                                     ^
[   31.069017]  ffff200002486600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.096521]  ffff200002486680: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
[   31.096528] ==================================================================
[   31.096533] Disabling lock debugging due to kernel taint

It appears that when trying to determine the length of the string in the alternate firmware path, we make the mistake of not handling the case where the firmware path is empty correctly. Since strlen(mp_path) can return 0, we'll end up accessing mp_path[-1] when the firmware_path isn't provided through the module arguments.

So, fix this by just setting the end char to '\0' by default, and only changing it if we have a non-zero length. Additionally, use strnlen() with BRCMF_FW_ALTPATH_LEN instead of strlen() just to be extra safe.

Signed-off-by Lyude Paul <[email protected]>
Fixes 2baa3aaee27f ("brcmfmac: introduce brcmf_fw_alloc_request() function")
Cc Hante Meuleman <[email protected]>
Cc Pieter-Paul Giesberts <[email protected]>
Cc Franky Lin <[email protected]>
Cc Arend van Spriel <[email protected]>
Cc Kalle Valo <[email protected]>
Cc Arend Van Spriel <[email protected]>
Cc Himanshu Jha <[email protected]>
Cc Dan Haab <[email protected]>
Cc Jia-Shyr Chuang <[email protected]>
Cc Ian Molton <[email protected]>
Cc <[email protected]> # v4.17+
Signed-off-by Lyude Paul <[email protected]>
---
 .../net/wireless/broadcom/brcm80211/brcmfmac/firmware.c   | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c +6 -2
index 9095b830ae4d..9927079a9ace 100644
@@ -641,8 +641,9 @@ brcmf_fw_alloc_request(u32 chip, u32 chiprev,
 	struct brcmf_fw_request *fwreq;
 	char chipname[12];
 	const char *mp_path;
+	size_t mp_path_len;
 	u32 i, j;
-	char end;
+	char end = '\0';
 	size_t reqsz;
 
 	for (i = 0; i < table_size; i++) {

@@ -667,7 +668,10 @@ brcmf_fw_alloc_request(u32 chip, u32 chiprev,
 		   mapping_table[i].fw_base, chipname);
 
 	mp_path = brcmf_mp_global.firmware_path;
-	end = mp_path[strlen(mp_path) - 1];
+	mp_path_len = strnlen(mp_path, BRCMF_FW_ALTPATH_LEN);
+	if (mp_path_len)
+		end = mp_path[mp_path_len - 1];
+
 	fwreq->n_items = n_fwnames;
 
 	for (j = 0; j < n_fwnames; j++) {
Signature · 1 line
2.19.1
#1 lore raw
Quoted 64 lines · Lyude Paul

I ended up tracking down some rather nasty issues with f2fs (and other filesystem modules) constantly crashing on my kernel down to a combination of out of bounds memory accesses, one of which was coming from brcmfmac during module load:

[   30.891382] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4356-sdio for chip BCM4356/2
[   30.894437] ==================================================================
[   30.901581] BUG: KASAN: global-out-of-bounds in brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.909935] Read of size 1 at addr ffff2000024865df by task kworker/6:2/387
[   30.916805]
[   30.918261] CPU: 6 PID: 387 Comm: kworker/6:2 Tainted: G           O      4.20.0-rc3Lyude-Test+ #19
[   30.927251] Hardware name: amlogic khadas-vim2/khadas-vim2, BIOS 2018.07-rc2-armbian 09/11/2018
[   30.935964] Workqueue: events brcmf_driver_register [brcmfmac]
[   30.941641] Call trace:
[   30.944058]  dump_backtrace+0x0/0x3e8
[   30.947676]  show_stack+0x14/0x20
[   30.950968]  dump_stack+0x130/0x1c4
[   30.954406]  print_address_description+0x60/0x25c
[   30.959066]  kasan_report+0x1b4/0x368
[   30.962683]  __asan_report_load1_noabort+0x18/0x20
[   30.967547]  brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.967639]  brcmf_sdio_probe+0x163c/0x2050 [brcmfmac]
[   30.978035]  brcmf_ops_sdio_probe+0x598/0xa08 [brcmfmac]
[   30.983254]  sdio_bus_probe+0x190/0x398
[   30.983270]  really_probe+0x2a0/0xa70
[   30.983296]  driver_probe_device+0x1b4/0x2d8
[   30.994901]  __driver_attach+0x200/0x280
[   30.994914]  bus_for_each_dev+0x10c/0x1a8
[   30.994925]  driver_attach+0x38/0x50
[   30.994935]  bus_add_driver+0x330/0x608
[   30.994953]  driver_register+0x140/0x388
[   31.013965]  sdio_register_driver+0x74/0xa0
[   31.014076]  brcmf_sdio_register+0x14/0x60 [brcmfmac]
[   31.023177]  brcmf_driver_register+0xc/0x18 [brcmfmac]
[   31.023209]  process_one_work+0x654/0x1080
[   31.032266]  worker_thread+0x4f0/0x1308
[   31.032286]  kthread+0x2a8/0x320
[   31.039254]  ret_from_fork+0x10/0x1c
[   31.039269]
[   31.044226] The buggy address belongs to the variable:
[   31.044351]  brcmf_firmware_path+0x11f/0xfffffffffffd3b40 [brcmfmac]
[   31.055601]
[   31.057031] Memory state around the buggy address:
[   31.061800]  ffff200002486480: 04 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
[   31.068983]  ffff200002486500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.068993] >ffff200002486580: 00 00 00 00 00 00 00 00 fa fa fa fa 00 00 00 00
[   31.068999]                                                     ^
[   31.069017]  ffff200002486600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.096521]  ffff200002486680: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
[   31.096528] ==================================================================
[   31.096533] Disabling lock debugging due to kernel taint

It appears that when trying to determine the length of the string in the alternate firmware path, we make the mistake of not handling the case where the firmware path is empty correctly. Since strlen(mp_path) can return 0, we'll end up accessing mp_path[-1] when the firmware_path isn't provided through the module arguments.

So, fix this by just setting the end char to '\0' by default, and only changing it if we have a non-zero length. Additionally, use strnlen() with BRCMF_FW_ALTPATH_LEN instead of strlen() just to be extra safe.

Signed-off-by Lyude Paul <[email protected]>
Quoted 13 lines
Fixes 2baa3aaee27f ("brcmfmac: introduce brcmf_fw_alloc_request() function")
Cc Hante Meuleman <[email protected]>
Cc Pieter-Paul Giesberts <[email protected]>
Cc Franky Lin <[email protected]>
Cc Arend van Spriel <[email protected]>
Cc Kalle Valo <[email protected]>
Cc Arend Van Spriel <[email protected]>
Cc Himanshu Jha <[email protected]>
Cc Dan Haab <[email protected]>
Cc Jia-Shyr Chuang <[email protected]>
Cc Ian Molton <[email protected]>
Cc <[email protected]> # v4.17+
Signed-off-by Lyude Paul <[email protected]>

Lyude's s-o-b is twice, I can fix that.

Arend, should I queue this to 4.20?

Signature · 1 line
Kalle Valo
#2 lore raw
In reply to Lyude Paul
Quoted 62 lines · Lyude Paul

I ended up tracking down some rather nasty issues with f2fs (and other filesystem modules) constantly crashing on my kernel down to a combination of out of bounds memory accesses, one of which was coming from brcmfmac during module load:

[   30.891382] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4356-sdio for chip BCM4356/2
[   30.894437] ==================================================================
[   30.901581] BUG: KASAN: global-out-of-bounds in brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.909935] Read of size 1 at addr ffff2000024865df by task kworker/6:2/387
[   30.916805]
[   30.918261] CPU: 6 PID: 387 Comm: kworker/6:2 Tainted: G           O      4.20.0-rc3Lyude-Test+ #19
[   30.927251] Hardware name: amlogic khadas-vim2/khadas-vim2, BIOS 2018.07-rc2-armbian 09/11/2018
[   30.935964] Workqueue: events brcmf_driver_register [brcmfmac]
[   30.941641] Call trace:
[   30.944058]  dump_backtrace+0x0/0x3e8
[   30.947676]  show_stack+0x14/0x20
[   30.950968]  dump_stack+0x130/0x1c4
[   30.954406]  print_address_description+0x60/0x25c
[   30.959066]  kasan_report+0x1b4/0x368
[   30.962683]  __asan_report_load1_noabort+0x18/0x20
[   30.967547]  brcmf_fw_alloc_request+0x42c/0x480 [brcmfmac]
[   30.967639]  brcmf_sdio_probe+0x163c/0x2050 [brcmfmac]
[   30.978035]  brcmf_ops_sdio_probe+0x598/0xa08 [brcmfmac]
[   30.983254]  sdio_bus_probe+0x190/0x398
[   30.983270]  really_probe+0x2a0/0xa70
[   30.983296]  driver_probe_device+0x1b4/0x2d8
[   30.994901]  __driver_attach+0x200/0x280
[   30.994914]  bus_for_each_dev+0x10c/0x1a8
[   30.994925]  driver_attach+0x38/0x50
[   30.994935]  bus_add_driver+0x330/0x608
[   30.994953]  driver_register+0x140/0x388
[   31.013965]  sdio_register_driver+0x74/0xa0
[   31.014076]  brcmf_sdio_register+0x14/0x60 [brcmfmac]
[   31.023177]  brcmf_driver_register+0xc/0x18 [brcmfmac]
[   31.023209]  process_one_work+0x654/0x1080
[   31.032266]  worker_thread+0x4f0/0x1308
[   31.032286]  kthread+0x2a8/0x320
[   31.039254]  ret_from_fork+0x10/0x1c
[   31.039269]
[   31.044226] The buggy address belongs to the variable:
[   31.044351]  brcmf_firmware_path+0x11f/0xfffffffffffd3b40 [brcmfmac]
[   31.055601]
[   31.057031] Memory state around the buggy address:
[   31.061800]  ffff200002486480: 04 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
[   31.068983]  ffff200002486500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.068993] >ffff200002486580: 00 00 00 00 00 00 00 00 fa fa fa fa 00 00 00 00
[   31.068999]                                                     ^
[   31.069017]  ffff200002486600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   31.096521]  ffff200002486680: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
[   31.096528] ==================================================================
[   31.096533] Disabling lock debugging due to kernel taint

It appears that when trying to determine the length of the string in the alternate firmware path, we make the mistake of not handling the case where the firmware path is empty correctly. Since strlen(mp_path) can return 0, we'll end up accessing mp_path[-1] when the firmware_path isn't provided through the module arguments.

So, fix this by just setting the end char to '\0' by default, and only changing it if we have a non-zero length. Additionally, use strnlen() with BRCMF_FW_ALTPATH_LEN instead of strlen() just to be extra safe.

Quoted 13 lines
Fixes 2baa3aaee27f ("brcmfmac: introduce brcmf_fw_alloc_request() function")
Cc Hante Meuleman <[email protected]>
Cc Pieter-Paul Giesberts <[email protected]>
Cc Franky Lin <[email protected]>
Cc Arend van Spriel <[email protected]>
Cc Kalle Valo <[email protected]>
Cc Arend Van Spriel <[email protected]>
Cc Himanshu Jha <[email protected]>
Cc Dan Haab <[email protected]>
Cc Jia-Shyr Chuang <[email protected]>
Cc Ian Molton <[email protected]>
Cc <[email protected]> # v4.17+
Signed-off-by Lyude Paul <[email protected]>

Patch applied to wireless-drivers-next.git, thanks.

b72c51a58e6d brcmfmac: Fix out of bounds memory access during fw load

Signature · 3 lines
https://patchwork.kernel.org/patch/10696609/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches