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

[syzbot]

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: syzbot+8a821b...@syzkaller.appspotmail.com

==================================================================
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


---
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[syzbot]

syzbot has bisected this bug to:

commit e9db4ef6bf4ca9894bb324c76e01b8f1a16b2650
Author: John Fastabend <john.fa...@gmail.com>
Date: Sat Jun 30 13:17:47 2018 +0000

bpf: sockhash fix omitted bucket lock in sock_close

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11bb4e3da00000
start commit: 045df37e Merge branch 'cxgb4-Reference-count-MPS-TCAM-entr..
git tree: net-next
final crash: https://syzkaller.appspot.com/x/report.txt?x=13bb4e3da00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15bb4e3da00000

kernel config: https://syzkaller.appspot.com/x/.config?x=dd16b8dc9d0d210c
dashboard link: https://syzkaller.appspot.com/bug?extid=8a821b383523654227bf

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1389f5b5a00000

Reported-by: syzbot+8a821b...@syzkaller.appspotmail.com
Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Eric Biggers]

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#syz fix: bpf: sockmap/tls, close can race with map free