From b72c51a58e6d63ef673ac96b8ab5bc98799c5f7b Mon Sep 17 00:00:00 2001 From: Lyude Paul Date: Sat, 24 Nov 2018 17:57:05 -0500 Subject: [PATCH] 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. Fixes: 2baa3aaee27f ("brcmfmac: introduce brcmf_fw_alloc_request() function") Cc: Hante Meuleman Cc: Pieter-Paul Giesberts Cc: Franky Lin Cc: Arend van Spriel Cc: Kalle Valo Cc: Arend Van Spriel Cc: Himanshu Jha Cc: Dan Haab Cc: Jia-Shyr Chuang Cc: Ian Molton Cc: # v4.17+ Signed-off-by: Lyude Paul Signed-off-by: Kalle Valo --- .../net/wireless/broadcom/brcm80211/brcmfmac/firmware.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c index 72d8c0c3c3a1..dad3c1c79038 100644 --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c @@ -708,8 +708,9 @@ 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++) { @@ -734,7 +735,10 @@ 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++) {