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BUG: KASAN: global-out-of-bounds in number+0x4b8/0x1100 lib/vsprintf.c:494
Read of size 1 at addr ffffffff85c02b51 by task syz.3.16/3553

CPU: 1 UID: 0 PID: 3553 Comm: syz.3.16 Not tainted 6.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x108/0x280 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 number+0x4b8/0x1100 lib/vsprintf.c:494
 pointer+0x739/0xe60 lib/vsprintf.c:2484
 vsnprintf+0x6f1/0x11d0 lib/vsprintf.c:2846
 seq_vprintf fs/seq_file.c:391 [inline]
 seq_printf+0x168/0x250 fs/seq_file.c:406
 show_partition+0x19c/0x2a0 block/genhd.c:892
 seq_read_iter+0x8af/0xb90 fs/seq_file.c:272
 proc_reg_read_iter+0x10c/0x1f0 fs/proc/inode.c:299
 copy_splice_read+0x5be/0xb50 fs/splice.c:365
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x3ae/0x9f0 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x233/0x350 fs/splice.c:1233
 do_sendfile+0x4a2/0x720 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x19f/0x200 fs/read_write.c:1410
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x8d/0x170 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f31fbd85d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f31fcbc4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f31fbf76080 RCX: 00007f31fbd85d29
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 00007f31fbe01b08 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000023b R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f31fbf76080 R15: 00007fff01f49828
 </TASK>

The buggy address belongs to the variable:
 hex_asc_upper+0x11/0x40

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5c02
flags: 0x80000000002000(reserved|node=0|zone=1)
raw: 0080000000002000 ffffea0000170088 ffffea0000170088 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffffffff85c02a00: 02 f9 f9 f9 00 02 f9 f9 00 04 f9 f9 00 03 f9 f9
 ffffffff85c02a80: 07 f9 f9 f9 00 00 04 f9 f9 f9 f9 f9 00 00 00 00
>ffffffff85c02b00: 00 00 01 f9 f9 f9 f9 f9 00 00 01 f9 f9 f9 f9 f9
                                                 ^
 ffffffff85c02b80: 00 04 f9 f9 02 f9 f9 f9 01 f9 f9 f9 00 f9 f9 f9
 ffffffff85c02c00: 00 f9 f9 f9 00 04 f9 f9 00 06 f9 f9 00 f9 f9 f9
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