Re: [BUG] staging: r8188eu: KASAN: slab-out-of-bounds in rtw_cmd_thread

From: Pavel Skripkin
Date: Sun Apr 24 2022 - 11:08:04 EST


Hi Solomon,

On 4/24/22 15:11, Solomon Tan wrote:
On Sun, Apr 24, 2022 at 12:00:12PM +0200, Michael Straube wrote:
Hi,

It looks like
commit 0afaa121813e ("staging: r8188eu: use in-kernel ieee channel")
intoduced a. See KASAN output below.

That commit replaced the use of struct rtw_ieee80211_channel with struct
ieee80211_channel.

There are several calls to memcpy that used sizeof(struct
rtw_ieee80211_channel)
and now use sizeof(struct ieee80211_channel) but the sizes of these two
structures are not equal.


Oh no. When does this issue get triggered?

regards,
Michael

dmesg:

==================================================================
[ 422.214237] BUG: KASAN: slab-out-of-bounds in rtw_cmd_thread+0x1e8/0x430
[r8188eu]
[ 422.214277] Write of size 3600 at addr ffff8881e149d200 by task
RTW_CMD_THREAD/2563

[ 422.214289] CPU: 11 PID: 2563 Comm: RTW_CMD_THREAD Tainted: G C OE
5.18.0-rc2-staging+ #47 94e3ca73bebf5b7fec506721475e4fff2a023bb9
[ 422.214301] Hardware name: Gigabyte Technology Co., Ltd. B550M S2H/B550M
S2H, BIOS F15a 02/16/2022
[ 422.214309] Call Trace:
[ 422.214313] <TASK>
[ 422.214317] dump_stack_lvl+0x45/0x5b
[ 422.214327] print_report.cold+0x5e/0x5dc
[ 422.214335] ? kasan_set_track+0x21/0x30
[ 422.214342] ? kasan_set_free_info+0x20/0x40
[ 422.214349] ? rtw_cmd_thread+0x1e8/0x430 [r8188eu
91924fe1575bf49b9b37985ffde2c585d847446d]
[ 422.214386] kasan_report+0xab/0x120
[ 422.214394] ? rtw_cmd_thread+0x1e8/0x430 [r8188eu
91924fe1575bf49b9b37985ffde2c585d847446d]
[ 422.214430] kasan_check_range+0xf6/0x1d0
[ 422.214436] memcpy+0x39/0x60
[ 422.214442] rtw_cmd_thread+0x1e8/0x430 [r8188eu
91924fe1575bf49b9b37985ffde2c585d847446d]
[ 422.214479] ? rtw_setassocsta_cmdrsp_callback+0xd0/0xd0 [r8188eu
91924fe1575bf49b9b37985ffde2c585d847446d]
[ 422.214516] kthread+0x15d/0x190
[ 422.214523] ? kthread_complete_and_exit+0x20/0x20
[ 422.214531] ret_from_fork+0x22/0x30
[ 422.214540] </TASK>

Sorry, I am not familiar with KASAN. How should I interpret this output?
I see the paragraph above has references to rtw_cmd_thread. I assume
that is its way of indicating that rtw_cmd_thread is the cause of the
problem, but the one below refers to other functions. I'm not sure where
I should start looking. I would start looking at `rtw_sitesurvey_cmd` and
`rtw_scan_ch_decision`, which call the memcpy on the
rtw_ieee80211_channel structure, but they are not on the call trace.


drivers/staging/r8188eu/core/rtw_cmd.c:276: memcpy() call.

As Michael said the sizes of structures do not mach and the memcpy writes below allocated buffer.



With regards,
Pavel Skripkin