On 8/11/19 10:36 AM, Hillf Danton wrote:
On Sun, 11 Aug 2019 08:24:09 +0800

syzbot has found a reproducer for the following crash on:

HEAD commit:    451577f3 Merge tag 'kbuild-fixes-v5.3-3' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=120850a6600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2031e7d221391b8a
dashboard link: https://syzkaller.appspot.com/bug?extid=bd3bba6ff3fcea7a6ec6
compiler:       clang version 9.0.0 (/home/glider/llvm/clang 
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=130ffe4a600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17137d2c600000

The bug was bisected to:

commit a0b0fd53e1e67639b303b15939b9c653dbe7a8c4
Author: Bart Van Assche <bvanass...@acm.org>
Date:   Thu Feb 14 23:00:46 2019 +0000

      locking/lockdep: Free lock classes that are no longer in use

Hey Bart, don't think it's related in any way to your commit. I'll allocate some
time on working on this issue today, thanks!

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=152f6a9da00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=172f6a9da00000
console output: https://syzkaller.appspot.com/x/log.txt?x=132f6a9da00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+bd3bba6ff3fcea7a6...@syzkaller.appspotmail.com
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in 

WARNING: CPU: 0 PID: 9604 at kernel/bpf/core.c:851 bpf_jit_free+0x1a8/0x1f0
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9604 Comm: kworker/0:5 Not tainted 5.3.0-rc3+ #71
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events bpf_prog_free_deferred
Call Trace:
   __dump_stack lib/dump_stack.c:77 [inline]
   dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
   panic+0x25c/0x799 kernel/panic.c:219
   __warn+0x22f/0x230 kernel/panic.c:576
   report_bug+0x190/0x290 lib/bug.c:186
BUG: unable to handle page fault for address: fffffbfff4001000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 21ffee067 P4D 21ffee067 PUD 21ffed067 PMD 936de067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9604 Comm: kworker/0:5 Not tainted 5.3.0-rc3+ #71
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events bpf_prog_free_deferred
RIP: 0010:bpf_get_prog_addr_region kernel/bpf/core.c:537 [inline]
RIP: 0010:bpf_tree_comp kernel/bpf/core.c:600 [inline]
RIP: 0010:__lt_find include/linux/rbtree_latch.h:115 [inline]
RIP: 0010:latch_tree_find include/linux/rbtree_latch.h:208 [inline]
RIP: 0010:bpf_prog_kallsyms_find kernel/bpf/core.c:674 [inline]
RIP: 0010:is_bpf_text_address+0x201/0x3b0 kernel/bpf/core.c:709
Code: 85 c4 f5 ff 4d 39 f4 76 10 e8 7b c2 f5 ff 49 83 c7 10 eb 46 0f 1f 44
00 00 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84
c0 75 7d 41 8b 1c 24 48 c1 e3 0c 4c 01 e3 48 89 df
RSP: 0018:ffff888097eff828 EFLAGS: 00010806
RAX: 1ffffffff4001000 RBX: 0000000000000001 RCX: dffffc0000000000
RDX: ffff88809f1e0280 RSI: ffffffffff7a5520 RDI: ffffffffa0008000
RBP: ffff888097eff860 R08: ffffffff817dc73b R09: 0000000000000001
R10: fffffbfff117be6d R11: 0000000000000000 R12: ffffffffa0008000
R13: 0000000000000000 R14: ffffffffff7a5520 R15: ffff88809a46b2f8
FS:  0000000000000000(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffbfff4001000 CR3: 0000000095d73000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:

Pair bpf_prog_kallsyms_del_all() with bpf_prog_free() to silence
WARNING at kernel/bpf/core.c:851, see __bpf_prog_release() in
net/core/filter.c for why.

--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1987,6 +1987,7 @@ void bpf_prog_free(struct bpf_prog *fp)
        struct bpf_prog_aux *aux = fp->aux;
+ bpf_prog_kallsyms_del_all(fp);
        INIT_WORK(&aux->work, bpf_prog_free_deferred);
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1328,7 +1328,6 @@ static void __bpf_prog_put(struct bpf_pr
                perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_UNLOAD, 0);
                /* bpf_prog_free_id() must be called first */
                bpf_prog_free_id(prog, do_idr_lock);
-               bpf_prog_kallsyms_del_all(prog);

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