On Wed, Apr 08, 2020 at 11:12:13AM -0400, Peter Xu wrote: > On Wed, Apr 08, 2020 at 05:58:48PM +0800, Hillf Danton wrote: > > > > On Wed, 08 Apr 2020 00:48:13 -0700 > > > syzbot found the following crash on: > > > > > > HEAD commit: 763dede1 Merge tag 'for-linus-5.7-rc1' of git://git.kernel.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12b919c7e00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=12205d036cec317f > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3be1a33f04dc782e9fd5 > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=142f3b8fe00000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159bd23fe00000 > > > > > > The bug was bisected to: > > > > > > commit 4426e945df588f2878affddf88a51259200f7e29 > > > Author: Peter Xu <peterx@xxxxxxxxxx> > > > Date: Thu Apr 2 04:08:49 2020 +0000 > > > > > > mm/gup: allow VM_FAULT_RETRY for multiple times > > > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1408ea9fe00000 > > > final crash: https://syzkaller.appspot.com/x/report.txt?x=1608ea9fe00000 > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1208ea9fe00000 > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+3be1a33f04dc782e9fd5@xxxxxxxxxxxxxxxxxxxxxxxxx > > > Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times") > > > > > > ------------[ cut here ]------------ > > > WARNING: CPU: 1 PID: 7094 at crypto/af_alg.c:404 af_alg_make_sg+0x399/0x400 crypto/af_alg.c:404 > > > Kernel panic - not syncing: panic_on_warn set ... > > > CPU: 1 PID: 7094 Comm: syz-executor037 Not tainted 5.6.0-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 > > > panic+0x2e3/0x75c kernel/panic.c:221 > > > __warn.cold+0x2f/0x35 kernel/panic.c:582 > > > report_bug+0x27b/0x2f0 lib/bug.c:195 > > > fixup_bug arch/x86/kernel/traps.c:175 [inline] > > > fixup_bug arch/x86/kernel/traps.c:170 [inline] > > > do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267 > > > do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286 > > > invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 > > > RIP: 0010:af_alg_make_sg+0x399/0x400 crypto/af_alg.c:404 > > > Code: 5c 24 2b 31 ff 89 de e8 c5 b9 f8 fd 84 db 74 0e e8 8c b8 f8 fd 48 8b 04 24 48 89 44 24 70 e8 7e b8 f8 fd 0f 0b e8 77 b8 f8 fd <0f> 0b c7 44 24 4c ea ff ff ff e9 4b ff ff ff 48 89 df e8 40 6e 36 > > > RSP: 0018:ffffc900018779a0 EFLAGS: 00010293 > > > RAX: ffff8880a16b65c0 RBX: ffff8880a4141220 RCX: ffffffff837a763d > > > RDX: 0000000000000000 RSI: ffffffff837a78f9 RDI: 0000000000000005 > > > RBP: 000000001fef2254 R08: ffff8880a16b65c0 R09: ffffed10142d6cb9 > > > R10: ffff8880a16b65c7 R11: ffffed10142d6cb8 R12: 0000000000000000 > > > R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000 > > > hash_sendmsg+0x45c/0xad0 crypto/algif_hash.c:94 > > > sock_sendmsg_nosec net/socket.c:652 [inline] > > > sock_sendmsg+0xcf/0x120 net/socket.c:672 > > > ____sys_sendmsg+0x6bf/0x7e0 net/socket.c:2362 > > > ___sys_sendmsg+0x100/0x170 net/socket.c:2416 > > > __sys_sendmsg+0xec/0x1b0 net/socket.c:2449 > > > do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 > > > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > > > Make gup feed back correct error code in case of bailout. > > > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -1325,8 +1325,11 @@ retry: > > * start trying again otherwise it can loop forever. > > */ > > > > - if (fatal_signal_pending(current)) > > + if (fatal_signal_pending(current)) { > > + if (!pages_done) > > + pages_done = -EINTR; > > break; > > + } > > > > *locked = 1; > > down_read(&mm->mmap_sem); > > > > CC Thomas too. > > Sorry for all these mess... > > Frankly speaking I didn't notice get_user_pages_fast() forbids > returning zero while __get_user_pages() allowed it... Ideally I think > the gup callers should check against ret>0 to know exactly how many > valid pages we've got, but it's not an excuse good enough... > > Hillf, would you mind kick the syzbot directly next time when post the > fix? I'll make bold to do that for you this time, Thanks! I got one extra "#"... Doing it again... #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master 8<-------------------------------------------------------------------- >From 380003a56efc125565143c91ee6cefd7b3eba869 Mon Sep 17 00:00:00 2001 From: Hillf Danton <hdanton@xxxxxxxx> Date: Wed, 8 Apr 2020 11:01:25 -0400 Subject: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal __get_user_pages_locked() will return 0 instead of -EINTR after commit 4426e945df588 which added extra code to allow gup detect fatal signal faster. Restore that behavior. CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Hillf Danton <hdanton@xxxxxxxx> [peterx: write commit message] Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- mm/gup.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index afce0bc47e70..6076df8e04a4 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1326,8 +1326,11 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, * start trying again otherwise it can loop forever. */ - if (fatal_signal_pending(current)) + if (fatal_signal_pending(current)) { + if (!pages_done) + pages_done = -EINTR; break; + } ret = down_read_killable(&mm->mmap_sem); if (ret) { -- 2.24.1 -- Peter Xu
