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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>
This commit is contained in:
Vasily Gorbik 2017-11-15 14:15:36 +01:00 committed by Martin Schwidefsky
parent 6470c0cc48
commit b192571d1a
1 changed files with 2 additions and 2 deletions
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4
arch/s390/kernel/dis.c
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@ -480,7 +480,7 @@ 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;
@ -543,7 +543,7 @@ 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");