[syzbot] [mm?] KASAN: slab-use-after-free Read in finish_fault

[syzbot] [mm?] KASAN: slab-use-after-free Read in finish_fault

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    d35b2284e966 Add linux-next specific files for 20240607
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=178b77ba980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d8bf5cd6bcca7343
dashboard link: https://syzkaller.appspot.com/bug?extid=d6e5c328862b5ae6cbfe
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=174c680a980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111b9696980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e0055a00a2cb/disk-d35b2284.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/192cbb8cf833/vmlinux-d35b2284.xz
kernel image: https://storage.googleapis.com/syzbot-assets/57804c9c9319/bzImage-d35b2284.xz

The issue was bisected to:

commit 1c05047ad01693ad92bdf8347fad3b5c2b25e8bb
Author: Baolin Wang <baolin.wang@linux.alibaba.com>
Date:   Tue Jun 4 10:17:45 2024 +0000

    mm: memory: extend finish_fault() to support large folio

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11267f94980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=13267f94980000
console output: https://syzkaller.appspot.com/x/log.txt?x=15267f94980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6e5c328862b5ae6cbfe@syzkaller.appspotmail.com
Fixes: 1c05047ad016 ("mm: memory: extend finish_fault() to support large folio")

==================================================================
BUG: KASAN: use-after-free in ptep_get include/linux/pgtable.h:317 [inline]
BUG: KASAN: use-after-free in ptep_get_lockless include/linux/pgtable.h:581 [inline]
BUG: KASAN: use-after-free in pte_range_none mm/memory.c:4409 [inline]
BUG: KASAN: use-after-free in finish_fault+0xf87/0x1460 mm/memory.c:4905
Read of size 8 at addr ffff88807bfb7000 by task syz-executor149/5117

CPU: 0 PID: 5117 Comm: syz-executor149 Not tainted 6.10.0-rc2-next-20240607-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:91 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:117
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 ptep_get include/linux/pgtable.h:317 [inline]
 ptep_get_lockless include/linux/pgtable.h:581 [inline]
 pte_range_none mm/memory.c:4409 [inline]
 finish_fault+0xf87/0x1460 mm/memory.c:4905
 do_read_fault mm/memory.c:5052 [inline]
 do_fault mm/memory.c:5178 [inline]
 do_pte_missing mm/memory.c:3948 [inline]
 handle_pte_fault+0x3db5/0x7130 mm/memory.c:5502
 __handle_mm_fault mm/memory.c:5645 [inline]
 handle_mm_fault+0x10df/0x1ba0 mm/memory.c:5810
 faultin_page mm/gup.c:1339 [inline]
 __get_user_pages+0x6ef/0x1590 mm/gup.c:1638
 populate_vma_page_range+0x264/0x330 mm/gup.c:2078
 __mm_populate+0x27a/0x460 mm/gup.c:2181
 mm_populate include/linux/mm.h:3442 [inline]
 __do_sys_remap_file_pages mm/mmap.c:3177 [inline]
 __se_sys_remap_file_pages+0x7a1/0x9a0 mm/mmap.c:3103
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff1cbb3e399
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff1cbad8238 EFLAGS: 00000246 ORIG_RAX: 00000000000000d8
RAX: ffffffffffffffda RBX: 00007ff1cbbc8318 RCX: 00007ff1cbb3e399
RDX: 0000000000000000 RSI: 0000000000200000 RDI: 00000000202ec000
RBP: 00007ff1cbbc8310 R08: 0000000000000000 R09: 00007ff1cbad86c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff1cbbc831c
R13: 0000000000000000 R14: 00007ffcff8e0350 R15: 00007ffcff8e0438
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7bfb7
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00007ed408 ffff8880b94448a0 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x440dc0(GFP_KERNEL_ACCOUNT|__GFP_COMP|__GFP_ZERO), pid 5097, tgid 5088 (syz-executor149), ts 55842453591, free_ts 55925905863
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1470
 prep_new_page mm/page_alloc.c:1478 [inline]
 get_page_from_freelist+0x2cbd/0x2d70 mm/page_alloc.c:3457
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4715
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2263
 pagetable_alloc_noprof include/linux/mm.h:2881 [inline]
 __pte_alloc_one_noprof include/asm-generic/pgalloc.h:70 [inline]
 pte_alloc_one+0x88/0x5d0 arch/x86/mm/pgtable.c:33
 do_fault_around mm/memory.c:5000 [inline]
 do_read_fault mm/memory.c:5039 [inline]
 do_fault mm/memory.c:5178 [inline]
 do_pte_missing mm/memory.c:3948 [inline]
 handle_pte_fault+0x2ba7/0x7130 mm/memory.c:5502
 __handle_mm_fault mm/memory.c:5645 [inline]
 handle_mm_fault+0x10df/0x1ba0 mm/memory.c:5810
 faultin_page mm/gup.c:1339 [inline]
 __get_user_pages+0x6ef/0x1590 mm/gup.c:1638
 populate_vma_page_range+0x264/0x330 mm/gup.c:2078
 __mm_populate+0x27a/0x460 mm/gup.c:2181
 mm_populate include/linux/mm.h:3442 [inline]
 __do_sys_remap_file_pages mm/mmap.c:3177 [inline]
 __se_sys_remap_file_pages+0x7a1/0x9a0 mm/mmap.c:3103
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5097 tgid 5088 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1089 [inline]
 free_unref_folios+0x103a/0x1b00 mm/page_alloc.c:2669
 folios_put_refs+0x76e/0x860 mm/swap.c:1020
 free_pages_and_swap_cache+0x5c8/0x690 mm/swap_state.c:335
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 exit_mmap+0x44f/0xc80 mm/mmap.c:3395
 __mmput+0x115/0x390 kernel/fork.c:1341
 exit_mm+0x220/0x310 kernel/exit.c:565
 do_exit+0x9aa/0x28e0 kernel/exit.c:861
 do_group_exit+0x207/0x2c0 kernel/exit.c:1023
 get_signal+0x16a1/0x1740 kernel/signal.c:2909
 arch_do_signal_or_restart+0x96/0x830 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807bfb6f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807bfb6f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807bfb7000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88807bfb7080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807bfb7100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
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#syz undup

Re: [syzbot] [mm?] KASAN: slab-use-after-free Read in finish_fault

[Baolin Wang]

On 2024/6/13 19:38, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    d35b2284e966 Add linux-next specific files for 20240607
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=178b77ba980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d8bf5cd6bcca7343
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6e5c328862b5ae6cbfe
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=174c680a980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111b9696980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/e0055a00a2cb/disk-d35b2284.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/192cbb8cf833/vmlinux-d35b2284.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/57804c9c9319/bzImage-d35b2284.xz
> 
> The issue was bisected to:
> 
> commit 1c05047ad01693ad92bdf8347fad3b5c2b25e8bb
> Author: Baolin Wang <baolin.wang@linux.alibaba.com>
> Date:   Tue Jun 4 10:17:45 2024 +0000
> 
>      mm: memory: extend finish_fault() to support large folio
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11267f94980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=13267f94980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15267f94980000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d6e5c328862b5ae6cbfe@syzkaller.appspotmail.com
> Fixes: 1c05047ad016 ("mm: memory: extend finish_fault() to support large folio")
> 
> ==================================================================
> BUG: KASAN: use-after-free in ptep_get include/linux/pgtable.h:317 [inline]
> BUG: KASAN: use-after-free in ptep_get_lockless include/linux/pgtable.h:581 [inline]
> BUG: KASAN: use-after-free in pte_range_none mm/memory.c:4409 [inline]
> BUG: KASAN: use-after-free in finish_fault+0xf87/0x1460 mm/memory.c:4905
> Read of size 8 at addr ffff88807bfb7000 by task syz-executor149/5117
> 
> CPU: 0 PID: 5117 Comm: syz-executor149 Not tainted 6.10.0-rc2-next-20240607-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:91 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:117
>   print_address_description mm/kasan/report.c:377 [inline]
>   print_report+0x169/0x550 mm/kasan/report.c:488
>   kasan_report+0x143/0x180 mm/kasan/report.c:601
>   ptep_get include/linux/pgtable.h:317 [inline]
>   ptep_get_lockless include/linux/pgtable.h:581 [inline]
>   pte_range_none mm/memory.c:4409 [inline]
>   finish_fault+0xf87/0x1460 mm/memory.c:4905
>   do_read_fault mm/memory.c:5052 [inline]
>   do_fault mm/memory.c:5178 [inline]
>   do_pte_missing mm/memory.c:3948 [inline]
>   handle_pte_fault+0x3db5/0x7130 mm/memory.c:5502
>   __handle_mm_fault mm/memory.c:5645 [inline]
>   handle_mm_fault+0x10df/0x1ba0 mm/memory.c:5810
>   faultin_page mm/gup.c:1339 [inline]
>   __get_user_pages+0x6ef/0x1590 mm/gup.c:1638
>   populate_vma_page_range+0x264/0x330 mm/gup.c:2078
>   __mm_populate+0x27a/0x460 mm/gup.c:2181
>   mm_populate include/linux/mm.h:3442 [inline]
>   __do_sys_remap_file_pages mm/mmap.c:3177 [inline]
>   __se_sys_remap_file_pages+0x7a1/0x9a0 mm/mmap.c:3103
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f

Thanks for reporting. I think the problem is I should also consider the 
pagetable of PMD size in case the pte entry overflows. I will fix this 
issue ASAP.

Re: [syzbot] [mm?] KASAN: slab-use-after-free Read in finish_fault

[Baolin Wang]

On 2024/6/13 20:08, Baolin Wang wrote:
> 
> 
> On 2024/6/13 19:38, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    d35b2284e966 Add linux-next specific files for 20240607
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=178b77ba980000
>> kernel config:  
>> https://syzkaller.appspot.com/x/.config?x=d8bf5cd6bcca7343
>> dashboard link: 
>> https://syzkaller.appspot.com/bug?extid=d6e5c328862b5ae6cbfe
>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for 
>> Debian) 2.40
>> syz repro:      
>> https://syzkaller.appspot.com/x/repro.syz?x=174c680a980000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111b9696980000
>>
>> Downloadable assets:
>> disk image: 
>> https://storage.googleapis.com/syzbot-assets/e0055a00a2cb/disk-d35b2284.raw.xz
>> vmlinux: 
>> https://storage.googleapis.com/syzbot-assets/192cbb8cf833/vmlinux-d35b2284.xz
>> kernel image: 
>> https://storage.googleapis.com/syzbot-assets/57804c9c9319/bzImage-d35b2284.xz
>>
>> The issue was bisected to:
>>
>> commit 1c05047ad01693ad92bdf8347fad3b5c2b25e8bb
>> Author: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Date:   Tue Jun 4 10:17:45 2024 +0000
>>
>>      mm: memory: extend finish_fault() to support large folio
>>
>> bisection log:  
>> https://syzkaller.appspot.com/x/bisect.txt?x=11267f94980000
>> final oops:     
>> https://syzkaller.appspot.com/x/report.txt?x=13267f94980000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=15267f94980000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the 
>> commit:
>> Reported-by: syzbot+d6e5c328862b5ae6cbfe@syzkaller.appspotmail.com
>> Fixes: 1c05047ad016 ("mm: memory: extend finish_fault() to support 
>> large folio")
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in ptep_get include/linux/pgtable.h:317 
>> [inline]
>> BUG: KASAN: use-after-free in ptep_get_lockless 
>> include/linux/pgtable.h:581 [inline]
>> BUG: KASAN: use-after-free in pte_range_none mm/memory.c:4409 [inline]
>> BUG: KASAN: use-after-free in finish_fault+0xf87/0x1460 mm/memory.c:4905
>> Read of size 8 at addr ffff88807bfb7000 by task syz-executor149/5117
>>
>> CPU: 0 PID: 5117 Comm: syz-executor149 Not tainted 
>> 6.10.0-rc2-next-20240607-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, 
>> BIOS Google 04/02/2024
>> Call Trace:
>>   <TASK>
>>   __dump_stack lib/dump_stack.c:91 [inline]
>>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:117
>>   print_address_description mm/kasan/report.c:377 [inline]
>>   print_report+0x169/0x550 mm/kasan/report.c:488
>>   kasan_report+0x143/0x180 mm/kasan/report.c:601
>>   ptep_get include/linux/pgtable.h:317 [inline]
>>   ptep_get_lockless include/linux/pgtable.h:581 [inline]
>>   pte_range_none mm/memory.c:4409 [inline]
>>   finish_fault+0xf87/0x1460 mm/memory.c:4905
>>   do_read_fault mm/memory.c:5052 [inline]
>>   do_fault mm/memory.c:5178 [inline]
>>   do_pte_missing mm/memory.c:3948 [inline]
>>   handle_pte_fault+0x3db5/0x7130 mm/memory.c:5502
>>   __handle_mm_fault mm/memory.c:5645 [inline]
>>   handle_mm_fault+0x10df/0x1ba0 mm/memory.c:5810
>>   faultin_page mm/gup.c:1339 [inline]
>>   __get_user_pages+0x6ef/0x1590 mm/gup.c:1638
>>   populate_vma_page_range+0x264/0x330 mm/gup.c:2078
>>   __mm_populate+0x27a/0x460 mm/gup.c:2181
>>   mm_populate include/linux/mm.h:3442 [inline]
>>   __do_sys_remap_file_pages mm/mmap.c:3177 [inline]
>>   __se_sys_remap_file_pages+0x7a1/0x9a0 mm/mmap.c:3103
>>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Thanks for reporting. I think the problem is I should also consider the 
> pagetable of PMD size in case the pte entry overflows. I will fix this 
> issue ASAP.

I create following fix to avoid beyonding the PMD pagetable size.

diff --git a/mm/memory.c b/mm/memory.c
index 54d7d2acdf39..92c61800dfb4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4878,13 +4878,16 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
                 pgoff_t idx = folio_page_idx(folio, page);
                 /* The page offset of vmf->address within the VMA. */
                 pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff;
+               /* The index of the entry in the pagetable for fault 
page. */
+               pgoff_t pte_off = pte_index(vmf->address);

                 /*
                  * Fallback to per-page fault in case the folio size in 
page
-                * cache beyond the VMA limits.
+                * cache beyond the VMA limits and PMD pagetable limits.
                  */
                 if (unlikely(vma_off < idx ||
-                            vma_off + (nr_pages - idx) > vma_pages(vma))) {
+                            vma_off + (nr_pages - idx) > vma_pages(vma) ||
+                            pte_off < idx || pte_off + (nr_pages - idx) 
 > PTRS_PER_PTE - 1)) {
                         nr_pages = 1;
                 } else {
                         /* Now we can set mappings for the whole large 
folio. */