Re: [syzbot] WARNING: kmalloc bug in bpf_check

On 9/3/21 5:01 PM, syzbot wrote:

Hello,

syzbot found the following issue on:

HEAD commit:    a9c9a6f741cd Merge tag 'scsi-misc' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13fd5915300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c84ed2c3f57ace
dashboard link: https://syzkaller.appspot.com/bug?extid=f3e749d4c662818ae439
compiler:       Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11e4cdf5300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ef3b33300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f3e749d4c662818ae439@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 8408 at mm/util.c:597 kvmalloc_node+0x108/0x110 mm/util.c:597
Modules linked in:
CPU: 0 PID: 8408 Comm: syz-executor221 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kvmalloc_node+0x108/0x110 mm/util.c:597
Code: ff 48 89 df 44 89 fe 44 89 f2 e8 a3 6e 17 00 48 89 c5 eb 05 e8 19 28 ce ff 48 89 e8 5b 41 5c 41 5e 41 5f 5d c3 e8 08 28 ce ff <0f> 0b 31 ed eb e9 66 90 41 56 53 49 89 f6 48 89 fb e8 f2 27 ce ff
RSP: 0018:ffffc900017ff210 EFLAGS: 00010293
RAX: ffffffff81b2b708 RBX: 0000000200004d00 RCX: ffff888013ded580
RDX: 0000000000000000 RSI: 0000000200004d00 RDI: 000000007fffffff
RBP: 0000000000000000 R08: ffffffff81b2b6ac R09: 00000000ffffffff
R10: fffff520002ffe15 R11: 0000000000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: 00000000ffffffff R15: 0000000000002dc0
FS:  0000000001386300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3e712d36c0 CR3: 00000000342e8000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 kvmalloc include/linux/mm.h:806 [inline]
 kvmalloc_array include/linux/mm.h:824 [inline]
 kvcalloc include/linux/mm.h:829 [inline]
 check_btf_line kernel/bpf/verifier.c:9925 [inline]
 check_btf_info kernel/bpf/verifier.c:10049 [inline]
 bpf_check+0xd634/0x150d0 kernel/bpf/verifier.c:13759
 bpf_prog_load kernel/bpf/syscall.c:2301 [inline]
 __sys_bpf+0x11181/0x126e0 kernel/bpf/syscall.c:4587
 __do_sys_bpf kernel/bpf/syscall.c:4691 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4689 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4689
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43f0a9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe831a89a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f0a9
RDX: 0000000000000078 RSI: 0000000020000500 RDI: 0000000000000005
RBP: 0000000000403090 R08: 0000000000000000 R09: 0000000000400488
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000403120
R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488


---
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As mentioned to Linus earlier, this bug comes after recent patch

commit 7661809d493b426e979f39ab512e3adf41fbcc69
Author: Linus Torvalds [off-list ref]
Date:   Wed Jul 14 09:45:49 2021 -0700

    mm: don't allow oversized kvmalloc() calls
    
    'kvmalloc()' is a convenience function for people who want to do a
    kmalloc() but fall back on vmalloc() if there aren't enough physically
    contiguous pages, or if the allocation is larger than what kmalloc()
    supports.
    
    However, let's make sure it doesn't get _too_ easy to do crazy things
    with it.  In particular, don't allow big allocations that could be due
    to integer overflow or underflow.  So make sure the allocation size fits
    in an 'int', to protect against trivial integer conversion issues.
    
    Acked-by: Willy Tarreau [off-list ref]
    Cc: Kees Cook [off-list ref]
    Signed-off-by: Linus Torvalds [off-list ref]