Subject: KASAN: use-after-free Read in corrupted (3)

From: syzbot <[email-masked]>
Date: Wed, 26 Jun 2019 04:37:05 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    045df37e Merge branch 'cxgb4-Reference-count-MPS-TCAM-entr..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13c6217ea00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dd16b8dc9d0d210c
dashboard link: https://syzkaller.appspot.com/bug?extid=8a821b383523654227bf
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1389f5b5a00000

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

==================================================================
BUG: KASAN: use-after-free in vsnprintf+0x1727/0x19a0 lib/vsprintf.c:2503
Read of size 8 at addr ffff8880952500a0 by task syz-executor.1/9180

CPU: 0 PID: 9180 Comm: syz-executor.1 Not tainted 5.2.0-rc5+ #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:

Allocated by task 8:
  save_stack+0x23/0x90 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+0xcf/0xe0 mm/kasan/common.c:462
  kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:497
  slab_post_alloc_hook mm/slab.h:437 [inline]
  slab_alloc mm/slab.c:3326 [inline]
  kmem_cache_alloc+0x11a/0x6f0 mm/slab.c:3488
  vm_area_dup+0x21/0x170 kernel/fork.c:343
  dup_mmap kernel/fork.c:528 [inline]
  dup_mm+0x8c4/0x13b0 kernel/fork.c:1341
  copy_mm kernel/fork.c:1397 [inline]
  copy_process.part.0+0x2cde/0x6790 kernel/fork.c:2032
  copy_process kernel/fork.c:1800 [inline]
  _do_fork+0x25d/0xfe0 kernel/fork.c:2369
  __do_sys_clone kernel/fork.c:2476 [inline]
  __se_sys_clone kernel/fork.c:2470 [inline]
  __x64_sys_clone+0xbf/0x150 kernel/fork.c:2470
  do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2502230480:
------------[ cut here ]------------
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected  
to SLAB object 'shmem_inode_cache' (offset 1040, size 1)!
WARNING: CPU: 0 PID: 9180 at mm/usercopy.c:74 usercopy_warn+0xeb/0x110  
mm/usercopy.c:74
Kernel panic - not syncing: panic_on_warn set ...
Shutting down cpus with NMI
Kernel Offset: disabled

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email-masked].

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches