Re: KASAN: slab-out-of-bounds Read in sctp_getsockopt

[Xin Long]

On Sat, Oct 27, 2018 at 1:38 AM syzbot
<syzbot+5da0d0a72a9e7d791748@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    bd6bf7c10484 Merge tag 'pci-v4.20-changes' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16fd6bcb400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2dd8629d56664133
> dashboard link: https://syzkaller.appspot.com/bug?extid=5da0d0a72a9e7d791748
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16b3ea33400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17f9f1bd400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+5da0d0a72a9e7d791748@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in sctp_getsockopt_pr_streamstatus
> net/sctp/socket.c:7174 [inline]
Forgot to change to use "&" in sctp_getsockopt_pr_streamstatus() in
"sctp: get pr_assoc and pr_stream all status with SCTP_PR_SCTP_ALL instead"

@@ -7158,7 +7158,7 @@ static int
sctp_getsockopt_pr_streamstatus(struct sock *sk, int len,
                goto out;
        }

-       if (policy == SCTP_PR_SCTP_ALL) {
+       if (policy & SCTP_PR_SCTP_ALL) {

> BUG: KASAN: slab-out-of-bounds in sctp_getsockopt+0x7516/0x7cc2
> net/sctp/socket.c:7582
> Read of size 8 at addr ffff8801d89f0968 by task syz-executor278/5330
>
> CPU: 1 PID: 5330 Comm: syz-executor278 Not tainted 4.19.0+ #303
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x244/0x39d lib/dump_stack.c:113
>   print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
>   kasan_report_error mm/kasan/report.c:354 [inline]
>   kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>   sctp_getsockopt_pr_streamstatus net/sctp/socket.c:7174 [inline]
>   sctp_getsockopt+0x7516/0x7cc2 net/sctp/socket.c:7582
>   sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
>   __sys_getsockopt+0x1ad/0x390 net/socket.c:1939
>   __do_sys_getsockopt net/socket.c:1950 [inline]
>   __se_sys_getsockopt net/socket.c:1947 [inline]
>   __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x445789
> Code: e8 6c b6 02 00 48 83 c4 18 c3 0f 1f 80 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 0f 83 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007effdb293db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
> RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 0000000000445789
> RDX: 0000000000000074 RSI: 0000000000000084 RDI: 0000000000000003
> RBP: 00000000006dac40 R08: 0000000020000040 R09: 0000000000000000
> R10: 0000000020000080 R11: 0000000000000246 R12: 00000000006dac4c
> R13: 00007ffcfc408c6f R14: 00007effdb2949c0 R15: 00000000006dad2c
>
> Allocated by task 5329:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
>   kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
>   kmalloc include/linux/slab.h:513 [inline]
>   kzalloc include/linux/slab.h:707 [inline]
>   sctp_stream_init_ext+0x4f/0xf0 net/sctp/stream.c:237
>   sctp_sendmsg_to_asoc+0x1308/0x1a20 net/sctp/socket.c:1896
>   sctp_sendmsg+0x13c2/0x1da0 net/sctp/socket.c:2113
>   inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>   __sys_sendto+0x3d7/0x670 net/socket.c:1788
>   __do_sys_sendto net/socket.c:1800 [inline]
>   __se_sys_sendto net/socket.c:1796 [inline]
>   __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 3223:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
>   kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>   __cache_free mm/slab.c:3498 [inline]
>   kfree+0xcf/0x230 mm/slab.c:3813
>   kzfree+0x28/0x30 mm/slab_common.c:1543
>   aa_free_file_ctx security/apparmor/include/file.h:76 [inline]
>   apparmor_file_free_security+0x133/0x1a0 security/apparmor/lsm.c:448
>   security_file_free+0x4a/0x80 security/security.c:900
>   file_free fs/file_table.c:54 [inline]
>   __fput+0x4e8/0xa30 fs/file_table.c:294
>   ____fput+0x15/0x20 fs/file_table.c:309
>   task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8801d89f0900
>   which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 8 bytes to the right of
>   96-byte region [ffff8801d89f0900, ffff8801d89f0960)
> The buggy address belongs to the page:
> page:ffffea0007627c00 count:1 mapcount:0 mapping:ffff8801da8004c0 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffffea0007646748 ffffea0007613488 ffff8801da8004c0
> raw: 0000000000000000 ffff8801d89f0000 0000000100000020 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8801d89f0800: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>   ffff8801d89f0880: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > ffff8801d89f0900: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>                                                            ^
>   ffff8801d89f0980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>   ffff8801d89f0a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
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>
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