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From:   Alexandre Ghiti <alexghiti@rivosinc.com>
Date:   Tue, 2 May 2023 15:13:11 +0200
Message-ID: <CAHVXubiYTtDx98E9kRyC8cFVrDPHu88SCGndyj06Eqs55K2cGQ@mail.gmail.com>
Subject: Re: [syzbot] [fs?] KASAN: stack-out-of-bounds Read in proc_pid_stack
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Alexandre Ghiti <alex@ghiti.fr>,
        syzbot <syzbot+01e9a564dc6b3289cea3@syzkaller.appspotmail.com>,
        brauner@kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Palmer Dabbelt <palmer@dabbelt.com>
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On Tue, May 2, 2023 at 2:50=E2=80=AFPM Dmitry Vyukov <dvyukov@google.com> w=
rote:
>
> On Tue, 2 May 2023 at 14:46, Alexandre Ghiti <alexghiti@rivosinc.com> wro=
te:
> > > > On 5/2/23 09:15, Dmitry Vyukov wrote:
> > > > > On Tue, 2 May 2023 at 09:05, syzbot
> > > > > <syzbot+01e9a564dc6b3289cea3@syzkaller.appspotmail.com> wrote:
> > > > >> Hello,
> > > > >>
> > > > >> syzbot found the following issue on:
> > > > >>
> > > > >> HEAD commit:    950b879b7f02 riscv: Fixup race condition on PG_d=
cache_clea..
> > > > >> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/ri=
scv/linux.git fixes
> > > > >> console output: https://syzkaller.appspot.com/x/log.txt?x=3D10c4=
c1f7c80000
> > > > >> kernel config:  https://syzkaller.appspot.com/x/.config?x=3Deceb=
ece1b90c0342
> > > > >> dashboard link: https://syzkaller.appspot.com/bug?extid=3D01e9a5=
64dc6b3289cea3
> > > > >> compiler:       riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 2=
0210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > >> userspace arch: riscv64
> > > > >>
> > > > >> Unfortunately, I don't have any reproducer for this issue yet.
> > > > >>
> > > > >> IMPORTANT: if you fix the issue, please add the following tag to=
 the commit:
> > > > >> Reported-by: syzbot+01e9a564dc6b3289cea3@syzkaller.appspotmail.c=
om
> > > > >>
> > > > >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > > > >> BUG: KASAN: stack-out-of-bounds in walk_stackframe+0x128/0x2fe a=
rch/riscv/kernel/stacktrace.c:58
> > > > >> Read of size 8 at addr ff200000030a79b0 by task syz-executor.1/7=
894
> > > > >>
> > > > >> CPU: 0 PID: 7894 Comm: syz-executor.1 Tainted: G        W       =
   6.2.0-rc1-syzkaller #0
> > > > >> Hardware name: riscv-virtio,qemu (DT)
> > > > >> Call Trace:
> > > > >> [<ffffffff8000b9ea>] dump_backtrace+0x2e/0x3c arch/riscv/kernel/=
stacktrace.c:121
> > > > >> [<ffffffff83402b96>] show_stack+0x34/0x40 arch/riscv/kernel/stac=
ktrace.c:127
> > > > >> [<ffffffff83442726>] __dump_stack lib/dump_stack.c:88 [inline]
> > > > >> [<ffffffff83442726>] dump_stack_lvl+0xe0/0x14c lib/dump_stack.c:=
106
> > > > >> [<ffffffff83409674>] print_address_description mm/kasan/report.c=
:306 [inline]
> > > > >> [<ffffffff83409674>] print_report+0x1e4/0x4c0 mm/kasan/report.c:=
417
> > > > >> [<ffffffff804ead14>] kasan_report+0xb8/0xe6 mm/kasan/report.c:51=
7
> > > > >> [<ffffffff804ebea4>] check_region_inline mm/kasan/generic.c:183 =
[inline]
> > > > >> [<ffffffff804ebea4>] __asan_load8+0x7e/0xa6 mm/kasan/generic.c:2=
56
> > > > >> [<ffffffff8000b782>] walk_stackframe+0x128/0x2fe arch/riscv/kern=
el/stacktrace.c:58
> > > > > +riscv maintainers
> > > > >
> > > > > I think this is an issue in riscv stack walking.
> > > > > If it's imprecise or walks stacks of running tasks, it needs to u=
se
> > > > > READ_ONCE_NOCHECK.
> > > > >
> > > > > #syz set subsystems: riscv
> > > >
> > > >
> > > > This fix was merged in 6.3: commit 76950340cf03 ("riscv: Use
> > > > READ_ONCE_NOCHECK in imprecise unwinding stack mode").
> > >
> > > Oh, I see, syzbot riscv build is still broken due to:
> > > https://syzkaller.appspot.com/bug?id=3D502e4cca2c3c985c2125ffa945b8e6=
36b7b100d7
> >
> > The fix for that was merged in 6.3-rc2 too (commit 2d311f480b52
> > ("riscv, bpf: Fix patch_text implicit declaration")): but the fixes
> > branch is still based on top of Linux 6.3-rc1 (Aleksandr mentioned
> > that already).
>
> Is riscv-fixes the right branch to test?
> Is there one that is updated regularly?
> syzbot generally requires a fresh tree. Provided there are dozens of
> bugs being found and fixed every week, if a tree becomes too old, it
> just produces already fixed bugs that waste time.

I would say that testing only the latest rcX is the best bet for us as
the fixes branch always lags on rc1, but @Palmer/@Conor may have
another opinion.

>
> https://lore.kernel.org/all/00000000000049382505ebef4a0c@google.com/T/#md=
2075a04dd463fefe31f73e098672a69d948a1ce
> >
> > That's weird, I think this one was merged in v6.1-rc2 (commit
> > 5c20a3a9df19 ("RISC-V: Fix compilation without RISCV_ISA_ZICBOM")).
> >
> > >
> > > so it still tests an older build.
> >
> > FYI, the latest fixes for KASAN were merged in 6.4 (or are about to).
> >
> > Thanks,
> >
> > Alex
> >
> > >
> > > #syz fix:
> > > riscv: Use READ_ONCE_NOCHECK in imprecise unwinding stack mode
> > >
> > > > >> [<ffffffff8000bc66>] arch_stack_walk+0x2c/0x3c arch/riscv/kernel=
/stacktrace.c:154
> > > > >> [<ffffffff80190822>] stack_trace_save_tsk+0x14a/0x1bc kernel/sta=
cktrace.c:150
> > > > >> [<ffffffff80697822>] proc_pid_stack+0x146/0x1ee fs/proc/base.c:4=
56
> > > > >> [<ffffffff80698bb0>] proc_single_show+0x9c/0x148 fs/proc/base.c:=
777
> > > > >> [<ffffffff805af580>] traverse.part.0+0x74/0x2ca fs/seq_file.c:11=
1
> > > > >> [<ffffffff805aff02>] traverse fs/seq_file.c:101 [inline]
> > > > >> [<ffffffff805aff02>] seq_read_iter+0x72c/0x934 fs/seq_file.c:195
> > > > >> [<ffffffff805b0224>] seq_read+0x11a/0x16e fs/seq_file.c:162
> > > > >> [<ffffffff805453ea>] do_loop_readv_writev fs/read_write.c:756 [i=
nline]
> > > > >> [<ffffffff805453ea>] do_loop_readv_writev fs/read_write.c:743 [i=
nline]
> > > > >> [<ffffffff805453ea>] do_iter_read+0x324/0x3c2 fs/read_write.c:79=
8
> > > > >> [<ffffffff805455f8>] vfs_readv+0xfe/0x166 fs/read_write.c:916
> > > > >> [<ffffffff80549c66>] do_preadv fs/read_write.c:1008 [inline]
> > > > >> [<ffffffff80549c66>] __do_sys_preadv fs/read_write.c:1058 [inlin=
e]
> > > > >> [<ffffffff80549c66>] sys_preadv+0x182/0x1fa fs/read_write.c:1053
> > > > >> [<ffffffff80005ff6>] ret_from_syscall+0x0/0x2
> > > > >>
> > > > >> The buggy address belongs to the virtual mapping at
> > > > >>   [ff200000030a0000, ff200000030a9000) created by:
> > > > >>   kernel_clone+0xee/0x914 kernel/fork.c:2681
> > > > >>
> > > > >> The buggy address belongs to the physical page:
> > > > >> page:ff1c0000024e5f00 refcount:1 mapcount:0 mapping:000000000000=
0000 index:0x0 pfn:0x9397c
> > > > >> memcg:ff6000000ffd7202
> > > > >> flags: 0xffe000000000000(node=3D0|zone=3D0|lastcpupid=3D0x7ff)
> > > > >> raw: 0ffe000000000000 0000000000000000 0000000000000122 00000000=
00000000
> > > > >> raw: 0000000000000000 0000000000000000 00000001ffffffff ff600000=
0ffd7202
> > > > >> page dumped because: kasan: bad access detected
> > > > >> page_owner tracks the page as allocated
> > > > >> page last allocated via order 0, migratetype Unmovable, gfp_mask=
 0x102dc2(GFP_HIGHUSER|__GFP_NOWARN|__GFP_ZERO), pid 7873, tgid 7873 (syz-e=
xecutor.1), ts 4012100669800, free_ts 4010400733200
> > > > >>   __set_page_owner+0x32/0x182 mm/page_owner.c:190
> > > > >>   set_page_owner include/linux/page_owner.h:31 [inline]
> > > > >>   post_alloc_hook+0xf8/0x11a mm/page_alloc.c:2524
> > > > >>   prep_new_page mm/page_alloc.c:2531 [inline]
> > > > >>   get_page_from_freelist+0xc0e/0x1118 mm/page_alloc.c:4283
> > > > >>   __alloc_pages+0x1b0/0x165a mm/page_alloc.c:5549
> > > > >>   alloc_pages+0x132/0x25e mm/mempolicy.c:2286
> > > > >>   vm_area_alloc_pages mm/vmalloc.c:2989 [inline]
> > > > >>   __vmalloc_area_node mm/vmalloc.c:3057 [inline]
> > > > >>   __vmalloc_node_range+0x81c/0xdb4 mm/vmalloc.c:3227
> > > > >>   alloc_thread_stack_node kernel/fork.c:311 [inline]
> > > > >>   dup_task_struct kernel/fork.c:987 [inline]
> > > > >>   copy_process+0x210e/0x4068 kernel/fork.c:2097
> > > > >>   kernel_clone+0xee/0x914 kernel/fork.c:2681
> > > > >>   __do_sys_clone+0xec/0x120 kernel/fork.c:2822
> > > > >>   sys_clone+0x32/0x44 kernel/fork.c:2790
> > > > >>   ret_from_syscall+0x0/0x2
> > > > >> page last free stack trace:
> > > > >>   __reset_page_owner+0x4a/0xf8 mm/page_owner.c:148
> > > > >>   reset_page_owner include/linux/page_owner.h:24 [inline]
> > > > >>   free_pages_prepare mm/page_alloc.c:1446 [inline]
> > > > >>   free_pcp_prepare+0x254/0x48e mm/page_alloc.c:1496
> > > > >>   free_unref_page_prepare mm/page_alloc.c:3369 [inline]
> > > > >>   free_unref_page_list+0x11e/0x736 mm/page_alloc.c:3510
> > > > >>   release_pages+0x85a/0xbb2 mm/swap.c:1076
> > > > >>   free_pages_and_swap_cache+0x76/0x88 mm/swap_state.c:311
> > > > >>   tlb_batch_pages_flush+0x86/0x10c mm/mmu_gather.c:97
> > > > >>   tlb_flush_mmu_free mm/mmu_gather.c:292 [inline]
> > > > >>   tlb_flush_mmu mm/mmu_gather.c:299 [inline]
> > > > >>   tlb_finish_mmu+0xcc/0x280 mm/mmu_gather.c:391
> > > > >>   exit_mmap+0x190/0x686 mm/mmap.c:3096
> > > > >>   __mmput+0x98/0x290 kernel/fork.c:1207
> > > > >>   mmput+0x74/0x88 kernel/fork.c:1229
> > > > >>   exit_mm kernel/exit.c:563 [inline]
> > > > >>   do_exit+0x602/0x17be kernel/exit.c:854
> > > > >>   do_group_exit+0x8e/0x15e kernel/exit.c:1012
> > > > >>   __do_sys_exit_group kernel/exit.c:1023 [inline]
> > > > >>   __wake_up_parent+0x0/0x4a kernel/exit.c:1021
> > > > >>   ret_from_syscall+0x0/0x2
> > > > >>
> > > > >> Memory state around the buggy address:
> > > > >>   ff200000030a7880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00=
 00
> > > > >>   ff200000030a7900: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 f2=
 f2
> > > > >>> ff200000030a7980: 00 00 00 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 =
00
> > > > >>                                       ^
> > > > >>   ff200000030a7a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00=
 00
> > > > >>   ff200000030a7a80: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1=
 f1
> > > > >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > > > >>
> > > > >>
> > > > >> ---
> > > > >> This report 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 syzkaller@googlegroups.com.
> > > > >>
> > > > >> syzbot will keep track of this issue. See:
> > > > >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > > > >>
> > > > >> If the bug is already fixed, let syzbot know by replying with:
> > > > >> #syz fix: exact-commit-title
> > > > >>
> > > > >> If you want to change bug's subsystems, reply with:
> > > > >> #syz set subsystems: new-subsystem
> > > > >> (See the list of subsystem names on the web dashboard)
> > > > >>
> > > > >> If the bug is a duplicate of another bug, reply with:
> > > > >> #syz dup: exact-subject-of-another-report
> > > > >>
> > > > >> If you want to undo deduplication, reply with:
> > > > >> #syz undup
> > > > >>
> > > > >> --
> > > > >> You received this message because you are subscribed to the Goog=
le Groups "syzkaller-bugs" group.
> > > > >> To unsubscribe from this group and stop receiving emails from it=
, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> > > > >> To view this discussion on the web visit https://groups.google.c=
om/d/msgid/syzkaller-bugs/00000000000084706805fab08e27%40google.com.
> > > > > _______________________________________________
> > > > > linux-riscv mailing list
> > > > > linux-riscv@lists.infradead.org
> > > > > http://lists.infradead.org/mailman/listinfo/linux-riscv