[syzbot] [fs?] KASAN: stack-out-of-bounds Read in proc_pid_stack

Conor Dooley conor.dooley at microchip.com
Tue May 2 05:43:52 PDT 2023 

On Tue, May 02, 2023 at 02:32:33PM +0200, Dmitry Vyukov wrote:
> On Tue, 2 May 2023 at 14:02, Alexandre Ghiti <alex at ghiti.fr> wrote:
> >
> > On 5/2/23 09:15, Dmitry Vyukov wrote:
> > > On Tue, 2 May 2023 at 09:05, syzbot
> > > <syzbot+01e9a564dc6b3289cea3 at syzkaller.appspotmail.com> wrote:
> > >> Hello,
> > >>
> > >> syzbot found the following issue on:
> > >>
> > >> HEAD commit:    950b879b7f02 riscv: Fixup race condition on PG_dcache_clea..
> > >> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
> > >> console output: https://syzkaller.appspot.com/x/log.txt?x=10c4c1f7c80000
> > >> kernel config:  https://syzkaller.appspot.com/x/.config?x=ecebece1b90c0342
> > >> dashboard link: https://syzkaller.appspot.com/bug?extid=01e9a564dc6b3289cea3
> > >> compiler:       riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, 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 at syzkaller.appspotmail.com
> > >>
> > >> ==================================================================
> > >> BUG: KASAN: stack-out-of-bounds in walk_stackframe+0x128/0x2fe arch/riscv/kernel/stacktrace.c:58
> > >> Read of size 8 at addr ff200000030a79b0 by task syz-executor.1/7894
> > >>
> > >> 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/stacktrace.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:517
> > >> [<ffffffff804ebea4>] check_region_inline mm/kasan/generic.c:183 [inline]
> > >> [<ffffffff804ebea4>] __asan_load8+0x7e/0xa6 mm/kasan/generic.c:256
> > >> [<ffffffff8000b782>] walk_stackframe+0x128/0x2fe arch/riscv/kernel/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 use
> > > 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=502e4cca2c3c985c2125ffa945b8e636b7b100d7

I think this one is correct, but

> https://lore.kernel.org/all/00000000000049382505ebef4a0c@google.com/T/#md2075a04dd463fefe31f73e098672a69d948a1ce

this isn't the right lore link. I think you meant:
https://lore.kernel.org/linux-riscv/CANp29Y5dbsSjd5q2TNJYgO5U1d6wu+XSSWR3PHWTX_efg7VyEA@mail.gmail.com/

The fix for that went through the bpf tree though:
https://lore.kernel.org/bpf/871qkh9zj8.fsf@all.your.base.are.belong.to.us/T/

Perhaps that is now fixed in mainline? I think riscv/fixes just needs to
be updated (it normally is after -rc1 I think) and things should be
good to go, no?

Cheers,
Conor.

> 
> so it still tests an older build.
> 
> #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/stacktrace.c:150
> > >> [<ffffffff80697822>] proc_pid_stack+0x146/0x1ee fs/proc/base.c:456
> > >> [<ffffffff80698bb0>] proc_single_show+0x9c/0x148 fs/proc/base.c:777
> > >> [<ffffffff805af580>] traverse.part.0+0x74/0x2ca fs/seq_file.c:111
> > >> [<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 [inline]
> > >> [<ffffffff805453ea>] do_loop_readv_writev fs/read_write.c:743 [inline]
> > >> [<ffffffff805453ea>] do_iter_read+0x324/0x3c2 fs/read_write.c:798
> > >> [<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 [inline]
> > >> [<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:0000000000000000 index:0x0 pfn:0x9397c
> > >> memcg:ff6000000ffd7202
> > >> flags: 0xffe000000000000(node=0|zone=0|lastcpupid=0x7ff)
> > >> raw: 0ffe000000000000 0000000000000000 0000000000000122 0000000000000000
> > >> raw: 0000000000000000 0000000000000000 00000001ffffffff ff6000000ffd7202
> > >> 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-executor.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
> > >> ==================================================================
> > >>
> > >>
> > >> ---
> > >> 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 at 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
> > >>
> > >> --
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> > > _______________________________________________
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