kernel BUG at mm/usercopy.c:102 -- pc : usercopy_abort

[Xiubo Li]

Hi guys,

We are hitting the same crash frequently recently with the latest kernel 
when testing kceph, and the call trace will be something likes:

[ 1580.034891] usercopy: Kernel memory exposure attempt detected from 
SLUB object 'kmalloc-192' (offset 82, size 499712)!^M
[ 1580.045866] ------------[ cut here ]------------^M
[ 1580.050551] kernel BUG at mm/usercopy.c:102!^M
^M
Entering kdb (current=0xffff8881211f5500, pid 172901) on processor 4 
Oops: (null)^M
due to oops @ 0xffffffff8138cabd^M
CPU: 4 PID: 172901 Comm: fsstress Tainted: G S 6.6.0-g623393c9d50c #1^M
Hardware name: Supermicro SYS-5018R-WR/X10SRW-F, BIOS 1.0c 09/07/2015^M
RIP: 0010:usercopy_abort+0x6d/0x80^M
Code: 4c 0f 44 d0 41 53 48 c7 c0 1c e9 13 82 48 c7 c6 71 62 13 82 48 0f 
45 f0 48 89 f9 48 c7 c7 f0 6b 1b 82 4c 89 d2 e8 63 2b df ff <0f> 0b 49 
c7 c1 44 c8 14 82 4d 89 cb 4d 89 c8 eb a5 66 90 f3 0f 1e^M
RSP: 0018:ffffc90006dfba88 EFLAGS: 00010246^M
RAX: 000000000000006a RBX: 000000000007a000 RCX: 0000000000000000^M
RDX: 0000000000000000 RSI: ffff88885fd1d880 RDI: ffff88885fd1d880^M
RBP: 000000000007a000 R08: 0000000000000000 R09: c0000000ffffdfff^M
R10: 0000000000000001 R11: ffffc90006dfb930 R12: 0000000000000001^M
R13: ffff8882b7bbed12 R14: ffff88827a375830 R15: ffff8882b7b44d12^M
FS:  00007fb24c859500(0000) GS:ffff88885fd00000(0000) 
knlGS:0000000000000000^M
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033^M
CR2: 000055c2bcf9eb00 CR3: 000000028956c005 CR4: 00000000001706e0^M
Call Trace:^M
 <TASK>^M
 ? kdb_main_loop+0x32c/0xa10^M
 ? kdb_stub+0x216/0x420^M
more>

You can see more detail in ceph tracker 
https://tracker.ceph.com/issues/64471.

I have seen someone has reported a similar issue one year ago but that 
has been fixed already, please see 
https://lore.kernel.org/linux-mm/CANn89iLaWZhrfyn8NBzdN1zQC0d47WC4_jvpwKQPoHwyCVueVQ@xxxxxxxxxxxxxx/T/.

Is it a known issue ?

Thanks

- Xiubo