On Thu, Jun 04, 2020 at 08:55:55PM -0700, Eric Biggers wrote: > Possibly a bug in lib/radix-tree.c? this_cpu_ptr() in radix_tree_node_alloc() > can be reached without a prior preempt_disable(). Or is the caller of > idr_alloc() doing something wrong?
Yes, the idr_alloc() call is plainly wrong: mutex_lock(&qrtr_port_lock); if (!*port) { rc = idr_alloc(&qrtr_ports, ipc, QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1, GFP_ATOMIC); If we can take a mutex lock, there's no excuse to be using GFP_ATOMIC. That (and the call slightly lower in the function) should be GFP_KERNEL as the minimal fix (below). I'll send a followup patch which converts this IDR to the XArray instead. diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c index 2d8d6131bc5f..d2547711d20c 100644 --- a/net/qrtr/qrtr.c +++ b/net/qrtr/qrtr.c @@ -692,15 +692,15 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) if (!*port) { rc = idr_alloc(&qrtr_ports, ipc, QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1, - GFP_ATOMIC); + GFP_KERNEL); if (rc >= 0) *port = rc; } else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) { rc = -EACCES; } else if (*port == QRTR_PORT_CTRL) { - rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_ATOMIC); + rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_KERNEL); } else { - rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_ATOMIC); + rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_KERNEL); if (rc >= 0) *port = rc; } > On Thu, Jun 04, 2020 at 07:02:18PM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: acf25aa6 Merge tag 'Smack-for-5.8' of git://github.com/csc.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=13d6307a100000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=5263d9b5bce03c67 > > dashboard link: https://syzkaller.appspot.com/bug?extid=3eec59e770685e3dc879 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15bd4c1e100000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1520c9de100000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+3eec59e770685e3dc...@syzkaller.appspotmail.com > > > > RAX: ffffffffffffffda RBX: 00007ffdf01d56d0 RCX: 00000000004406c9 > > RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003 > > RBP: 0000000000000005 R08: 0000000000000001 R09: 0000000000000031 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f50 > > R13: 0000000000401fe0 R14: 0000000000000000 R15: 0000000000000000 > > BUG: using smp_processor_id() in preemptible [00000000] code: > > syz-executor036/6796 > > caller is radix_tree_node_alloc.constprop.0+0x200/0x330 lib/radix-tree.c:262 > > CPU: 0 PID: 6796 Comm: syz-executor036 Not tainted 5.7.0-syzkaller #0 > > 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+0x188/0x20d lib/dump_stack.c:118 > > check_preemption_disabled lib/smp_processor_id.c:47 [inline] > > debug_smp_processor_id.cold+0x88/0x9b lib/smp_processor_id.c:57 > > radix_tree_node_alloc.constprop.0+0x200/0x330 lib/radix-tree.c:262 > > radix_tree_extend+0x256/0x4e0 lib/radix-tree.c:424 > > idr_get_free+0x60c/0x8e0 lib/radix-tree.c:1492 > > idr_alloc_u32+0x170/0x2d0 lib/idr.c:46 > > idr_alloc+0xc2/0x130 lib/idr.c:87 > > qrtr_port_assign net/qrtr/qrtr.c:703 [inline] > > __qrtr_bind.isra.0+0x12e/0x5c0 net/qrtr/qrtr.c:756 > > qrtr_autobind net/qrtr/qrtr.c:787 [inline] > > qrtr_autobind+0xaf/0xf0 net/qrtr/qrtr.c:775 > > qrtr_sendmsg+0x1d6/0x770 net/qrtr/qrtr.c:895 > > sock_sendmsg_nosec net/socket.c:652 [inline] > > sock_sendmsg+0xcf/0x120 net/socket.c:672 > > ____sys_sendmsg+0x6e6/0x810 net/socket.c:2352 > > ___sys_sendmsg+0x100/0x170 net/socket.c:2406 > > __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439 > > do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 > > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > RIP: 0033:0x4406c9 > > Code: 25 02 00 85 c0 b8 00 00 00 00 48 0f 44 c3 5b c3 90 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007ffdf01d56c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e > > RAX: ffffffffffffffda RBX: 00007ffdf01d56d0 RCX: 00000000004406c9 > > RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003 > > RBP: 0000000000000005 R08: 0000000000000001 R09: 0000000000000031 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f50 > > R13: 0000000000401fe0 R14: 0000000000000000 R15: 0000000000000000 > > > > > > --- > > 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 syzkal...@googlegroups.com. > > > > 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 > >