From: Vasily Gorbik <gor@linux.vnet.ibm.com>
Subject: s390/disassembler: increase show_code buffer size
Patch-mainline: v4.15-rc1
Git-commit: b192571d1ae375e0bbe0aa3ccfa1a3c3704454b9
References: bnc#1072915, LTC#161577
Description: disassembler: possible stack corruption during dump_stack
Symptom: potential crash after the kernel stack trace
Problem: Current buffer size of 64 is too small. objdump shows
that there are instructions which would require up to
75 bytes buffer (with current formating).
Solution: Increase the buffer size from 64 to 128 bytes,
replace some spaces with a tab.
Reproduction: The issue has been noticed due to kasan report.
The core dump triggered via
'echo c > /proc/sysrq-trigger' produces the kernel
stack trace log which overflows the buffer.
Upstream-Description:
s390/disassembler: increase show_code buffer size
Current buffer size of 64 is too small. objdump shows that there are
instructions which would require up to 75 bytes buffer (with current
formating). 128 bytes "ought to be enough for anybody".
Also replaces 8 spaces with a single tab to reduce the memory footprint.
Fixes the following KASAN finding:
BUG: KASAN: stack-out-of-bounds in number+0x3fe/0x538
Write of size 1 at addr 000000005a4a75a0 by task bash/1282
CPU: 1 PID: 1282 Comm: bash Not tainted 4.14.0+ #215
Hardware name: IBM 2964 N96 702 (z/VM 6.4.0)
Call Trace:
([<000000000011eeb6>] show_stack+0x56/0x88)
[<0000000000e1ce1a>] dump_stack+0x15a/0x1b0
[<00000000004e2994>] print_address_description+0xf4/0x288
[<00000000004e2cf2>] kasan_report+0x13a/0x230
[<0000000000e38ae6>] number+0x3fe/0x538
[<0000000000e3dfe4>] vsnprintf+0x194/0x948
[<0000000000e3ea42>] sprintf+0xa2/0xb8
[<00000000001198dc>] print_insn+0x374/0x500
[<0000000000119346>] show_code+0x4ee/0x538
[<000000000011f234>] show_registers+0x34c/0x388
[<000000000011f2ae>] show_regs+0x3e/0xa8
[<000000000011f502>] die+0x1ea/0x2e8
[<0000000000138f0e>] do_no_context+0x106/0x168
[<0000000000139a1a>] do_protection_exception+0x4da/0x7d0
[<0000000000e55914>] pgm_check_handler+0x16c/0x1c0
[<000000000090639e>] sysrq_handle_crash+0x46/0x58
([<0000000000000007>] 0x7)
[<00000000009073fa>] __handle_sysrq+0x102/0x218
[<0000000000907c06>] write_sysrq_trigger+0xd6/0x100
[<000000000061d67a>] proc_reg_write+0xb2/0x128
[<0000000000520be6>] __vfs_write+0xee/0x368
[<0000000000521222>] vfs_write+0x21a/0x278
[<000000000052156a>] SyS_write+0xda/0x178
[<0000000000e555cc>] system_call+0xc4/0x270
The buggy address belongs to the page:
page:000003d1016929c0 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x0()
raw: 0000000000000000 0000000000000000 0000000000000000 ffffffff00000000
raw: 0000000000000100 0000000000000200 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
000000005a4a7480: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
000000005a4a7500: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00
>000000005a4a7580: 00 00 00 00 f3 f3 f3 f3 00 00 00 00 00 00 00 00
^
000000005a4a7600: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f8 f8
000000005a4a7680: f2 f2 f2 f2 f2 f2 f8 f8 f2 f2 f3 f3 f3 f3 00 00
==================================================================
Cc: <stable@vger.kernel.org>
Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com>
Acked-by: Johannes Thumshirn <jthumshirn@suse.de>
---
arch/s390/kernel/dis.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/s390/kernel/dis.c
+++ b/arch/s390/kernel/dis.c
@@ -1953,7 +1953,7 @@ void show_code(struct pt_regs *regs)
{
char *mode = user_mode(regs) ? "User" : "Krnl";
unsigned char code[64];
- char buffer[64], *ptr;
+ char buffer[128], *ptr;
mm_segment_t old_fs;
unsigned long addr;
int start, end, opsize, hops, i;
@@ -2016,7 +2016,7 @@ void show_code(struct pt_regs *regs)
start += opsize;
pr_cont("%s", buffer);
ptr = buffer;
- ptr += sprintf(ptr, "\n ");
+ ptr += sprintf(ptr, "\n\t ");
hops++;
}
pr_cont("\n");