Subject: Re: KASAN: slab-out-of-bounds Read in p54u_load_firmware_cb

From: syzbot <[email-masked]>
Date: Wed, 19 Jun 2019 19:20:05 -0700

syzbot has found a reproducer for the following crash on:

HEAD commit:    9939f56e usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=135e29faa00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df134eda130bb43a
dashboard link: https://syzkaller.appspot.com/bug?extid=6d237e74cdc13f036473
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=175d946ea00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

usb 3-1: Direct firmware load for isl3887usb failed with error -2
usb 3-1: Firmware not found.
==================================================================
BUG: KASAN: slab-out-of-bounds in p54u_load_firmware_cb.cold+0x97/0x13d  
drivers/net/wireless/intersil/p54/p54usb.c:936
Read of size 8 at addr ffff8881c9cf7588 by task kworker/1:5/2759

CPU: 1 PID: 2759 Comm: kworker/1:5 Not tainted 5.2.0-rc5+ #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events request_firmware_work_func
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xca/0x13e lib/dump_stack.c:113
  print_address_description+0x67/0x231 mm/kasan/report.c:188
  __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
  kasan_report+0xe/0x20 mm/kasan/common.c:614
  p54u_load_firmware_cb.cold+0x97/0x13d  
drivers/net/wireless/intersil/p54/p54usb.c:936
  request_firmware_work_func+0x126/0x242  
drivers/base/firmware_loader/main.c:785
  process_one_work+0x905/0x1570 kernel/workqueue.c:2269
  worker_thread+0x96/0xe20 kernel/workqueue.c:2415
  kthread+0x30b/0x410 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 1612:
  save_stack+0x1b/0x80 mm/kasan/common.c:71
  set_track mm/kasan/common.c:79 [inline]
  __kasan_kmalloc mm/kasan/common.c:489 [inline]
  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:462
  kmalloc include/linux/slab.h:547 [inline]
  syslog_print kernel/printk/printk.c:1346 [inline]
  do_syslog kernel/printk/printk.c:1519 [inline]
  do_syslog+0x4f4/0x12e0 kernel/printk/printk.c:1493
  kmsg_read+0x8a/0xb0 fs/proc/kmsg.c:40
  proc_reg_read+0x1c1/0x280 fs/proc/inode.c:221
  __vfs_read+0x76/0x100 fs/read_write.c:425
  vfs_read+0x18e/0x3d0 fs/read_write.c:461
  ksys_read+0x127/0x250 fs/read_write.c:587
  do_syscall_64+0xb7/0x560 arch/x86/entry/common.c:301
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 1612:
  save_stack+0x1b/0x80 mm/kasan/common.c:71
  set_track mm/kasan/common.c:79 [inline]
  __kasan_slab_free+0x130/0x180 mm/kasan/common.c:451
  slab_free_hook mm/slub.c:1421 [inline]
  slab_free_freelist_hook mm/slub.c:1448 [inline]
  slab_free mm/slub.c:2994 [inline]
  kfree+0xd7/0x280 mm/slub.c:3949
  syslog_print kernel/printk/printk.c:1405 [inline]
  do_syslog kernel/printk/printk.c:1519 [inline]
  do_syslog+0xff3/0x12e0 kernel/printk/printk.c:1493
  kmsg_read+0x8a/0xb0 fs/proc/kmsg.c:40
  proc_reg_read+0x1c1/0x280 fs/proc/inode.c:221
  __vfs_read+0x76/0x100 fs/read_write.c:425
  vfs_read+0x18e/0x3d0 fs/read_write.c:461
  ksys_read+0x127/0x250 fs/read_write.c:587
  do_syscall_64+0xb7/0x560 arch/x86/entry/common.c:301
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881c9cf7180
  which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 8 bytes to the right of
  1024-byte region [ffff8881c9cf7180, ffff8881c9cf7580)
The buggy address belongs to the page:
page:ffffea0007273d00 refcount:1 mapcount:0 mapping:ffff8881dac02a00  
index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 dead000000000100 dead000000000200 ffff8881dac02a00
raw: 0000000000000000 00000000000e000e 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881c9cf7480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881c9cf7500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881c9cf7580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                       ^
  ffff8881c9cf7600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881c9cf7680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================