[syzbot] KASAN: use-after-free Read in __vma_adjust

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=116194eff00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=68771c0e74f7bb7804e5
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12e632bbf00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=103df80ff00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+68771c...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __vma_adjust+0x18ee/0x1900 mm/mmap.c:763
Read of size 8 at addr ffff88801fefe208 by task syz-executor408/3621

CPU: 0 PID: 3621 Comm: syz-executor408 Not tainted 5.19.0-rc1-next-20220610-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
print_report mm/kasan/report.c:429 [inline]
kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
__vma_adjust+0x18ee/0x1900 mm/mmap.c:763
vma_merge+0x590/0x870 mm/mmap.c:1119
userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
__fput+0x277/0x9d0 fs/file_table.c:317
task_work_run+0xdd/0x1a0 kernel/task_work.c:177
ptrace_notify+0x114/0x140 kernel/signal.c:2353
ptrace_report_syscall include/linux/ptrace.h:420 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
syscall_exit_work kernel/entry/common.c:249 [inline]
syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
__syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f2d02e9ef59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 71 15 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2d02e502f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 00007f2d02f284a8 RCX: 00007f2d02e9ef59
RDX: 000000000000003c RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007f2d02f284a0 R08: 0000000000000001 R09: 0000000000000034
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2d02e50300
R13: 0000000000000001 R14: 00007f2d02e50400 R15: 0000000000022000
</TASK>

Allocated by task 3619:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:436 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
kasan_slab_alloc include/linux/kasan.h:224 [inline]
slab_post_alloc_hook mm/slab.h:750 [inline]
slab_alloc_node mm/slub.c:3214 [inline]
slab_alloc mm/slub.c:3222 [inline]
__kmem_cache_alloc_lru mm/slub.c:3229 [inline]
kmem_cache_alloc+0x204/0x3b0 mm/slub.c:3239
vm_area_dup+0x81/0x380 kernel/fork.c:466
dup_mmap+0x656/0x1090 kernel/fork.c:640
dup_mm+0x91/0x370 kernel/fork.c:1520
copy_mm kernel/fork.c:1569 [inline]
copy_process+0x3c95/0x7080 kernel/fork.c:2234
kernel_clone+0xe7/0xab0 kernel/fork.c:2649
__do_sys_clone+0xba/0x100 kernel/fork.c:2783
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 3621:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:45
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
kasan_slab_free include/linux/kasan.h:200 [inline]
slab_free_hook mm/slub.c:1727 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
slab_free mm/slub.c:3507 [inline]
kmem_cache_free+0xdd/0x5a0 mm/slub.c:3524
__vma_adjust+0x9ab/0x1900 mm/mmap.c:886
vma_merge+0x590/0x870 mm/mmap.c:1119
userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
__fput+0x277/0x9d0 fs/file_table.c:317
task_work_run+0xdd/0x1a0 kernel/task_work.c:177
ptrace_notify+0x114/0x140 kernel/signal.c:2353
ptrace_report_syscall include/linux/ptrace.h:420 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
syscall_exit_work kernel/entry/common.c:249 [inline]
syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
__syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff88801fefe1b0
which belongs to the cache vm_area_struct of size 152
The buggy address is located 88 bytes inside of
152-byte region [ffff88801fefe1b0, ffff88801fefe248)

The buggy address belongs to the physical page:
page:ffffea00007fbf80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1fefe
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea00009ed380 dead000000000003 ffff888140006b40
raw: 0000000000000000 0000000000120012 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 3327, tgid 3327 (rm), ts 28524505479, free_ts 28520297867
prep_new_page mm/page_alloc.c:2460 [inline]
get_page_from_freelist+0xa64/0x3d10 mm/page_alloc.c:4279
__alloc_pages+0x1c7/0x510 mm/page_alloc.c:5500
alloc_pages+0x1aa/0x310 mm/mempolicy.c:2279
alloc_slab_page mm/slub.c:1797 [inline]
allocate_slab+0x26c/0x3c0 mm/slub.c:1942
new_slab mm/slub.c:2002 [inline]
___slab_alloc+0x985/0xd90 mm/slub.c:3002
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
slab_alloc_node mm/slub.c:3180 [inline]
slab_alloc mm/slub.c:3222 [inline]
__kmem_cache_alloc_lru mm/slub.c:3229 [inline]
kmem_cache_alloc+0x360/0x3b0 mm/slub.c:3239
vm_area_dup+0x81/0x380 kernel/fork.c:466
__split_vma+0x9f/0x530 mm/mmap.c:2273
do_mas_align_munmap+0x2c0/0xf00 mm/mmap.c:2399
do_mas_munmap+0x202/0x2c0 mm/mmap.c:2556
mmap_region+0x219/0x1bf0 mm/mmap.c:2604
do_mmap+0x825/0xf60 mm/mmap.c:1480
vm_mmap_pgoff+0x1b7/0x290 mm/util.c:520
ksys_mmap_pgoff+0x40d/0x5a0 mm/mmap.c:1526
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1375 [inline]
free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1425
free_unref_page_prepare mm/page_alloc.c:3311 [inline]
free_unref_page_list+0x184/0x1530 mm/page_alloc.c:3475
release_pages+0xff1/0x2290 mm/swap.c:980
tlb_batch_pages_flush+0xa8/0x1a0 mm/mmu_gather.c:58
tlb_flush_mmu_free mm/mmu_gather.c:255 [inline]
tlb_flush_mmu mm/mmu_gather.c:262 [inline]
tlb_finish_mmu+0x147/0x7e0 mm/mmu_gather.c:353
exit_mmap+0x217/0x750 mm/mmap.c:3205
__mmput+0x128/0x4c0 kernel/fork.c:1180
mmput+0x5c/0x70 kernel/fork.c:1201
exec_mmap fs/exec.c:1038 [inline]
begin_new_exec+0xfbd/0x2e50 fs/exec.c:1297
load_elf_binary+0x15a3/0x4ec0 fs/binfmt_elf.c:1002
search_binary_handler fs/exec.c:1728 [inline]
exec_binprm fs/exec.c:1769 [inline]
bprm_execve fs/exec.c:1838 [inline]
bprm_execve+0x7ef/0x1970 fs/exec.c:1800
do_execveat_common+0x724/0x890 fs/exec.c:1943
do_execve fs/exec.c:2017 [inline]
__do_sys_execve fs/exec.c:2093 [inline]
__se_sys_execve fs/exec.c:2088 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:
ffff88801fefe100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
ffff88801fefe180: fc fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb
>ffff88801fefe200: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
^
ffff88801fefe280: fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88801fefe300: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
==================================================================


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has bisected this issue to:

commit d3ccd17e7c9647b956d415acdf3e3fde7ae9e20c
Author: Liam R. Howlett <Liam.H...@Oracle.com>
Date: Thu Jun 9 20:57:09 2022 +0000

mm: start tracking VMAs with maple tree

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11463853f00000
start commit: 6d0c80680317 Add linux-next specific files for 20220610
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=13463853f00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15463853f00000

kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=68771c0e74f7bb7804e5

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12e632bbf00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=103df80ff00000

Reported-by: syzbot+68771c...@syzkaller.appspotmail.com
Fixes: d3ccd17e7c96 ("mm: start tracking VMAs with maple tree")

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

[Hillf Danton]

On Sun, 12 Jun 2022 03:38:30 -0700

See if it is due to trying again without validating pointers.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 6d0c80680317

--- y/mm/mmap.c
+++ m/mm/mmap.c
@@ -674,6 +674,7 @@ int __vma_adjust(struct vm_area_struct *
int remove_next = 0;
MA_STATE(mas, &mm->mm_mt, 0, 0);
struct vm_area_struct *exporter = NULL, *importer = NULL;
+ bool valid_ptr = true;

if (next && !insert) {
if (end >= next->vm_end) {
@@ -760,6 +761,8 @@ again:
vma_adjust_trans_huge(orig_vma, start, end, adjust_next);

if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+ if (!valid_ptr)
+ return -ENOMEM;
if (exporter && exporter->anon_vma)
unlink_anon_vmas(importer);
return -ENOMEM;
@@ -915,6 +918,7 @@ again:
mas_reset(&mas);
remove_next = 1;
end = next->vm_end;
+ valid_ptr = false;
goto again;
}
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Write in userfaultfd_release

==================================================================
BUG: KASAN: use-after-free in userfaultfd_release+0x651/0x670 fs/userfaultfd.c:897
Write of size 8 at addr ffff8880781dfe78 by task syz-executor.0/4090

CPU: 0 PID: 4090 Comm: syz-executor.0 Not tainted 5.19.0-rc1-next-20220610-syzkaller-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
print_report mm/kasan/report.c:429 [inline]
kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491

userfaultfd_release+0x651/0x670 fs/userfaultfd.c:897

__fput+0x277/0x9d0 fs/file_table.c:317
task_work_run+0xdd/0x1a0 kernel/task_work.c:177

get_signal+0x1c5/0x2600 kernel/signal.c:2634
arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f734c489109
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f734d629168 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 00007f734c59bf60 RCX: 00007f734c489109

RDX: 000000000000003c RSI: 0000000020000180 RDI: 0000000000000003

RBP: 00007f734d6291d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffcee01460f R14: 00007f734d629300 R15: 0000000000022000
</TASK>

Allocated by task 4069:

kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:436 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
kasan_slab_alloc include/linux/kasan.h:224 [inline]
slab_post_alloc_hook mm/slab.h:750 [inline]
slab_alloc_node mm/slub.c:3214 [inline]
slab_alloc mm/slub.c:3222 [inline]
__kmem_cache_alloc_lru mm/slub.c:3229 [inline]
kmem_cache_alloc+0x204/0x3b0 mm/slub.c:3239
vm_area_dup+0x81/0x380 kernel/fork.c:466
dup_mmap+0x656/0x1090 kernel/fork.c:640
dup_mm+0x91/0x370 kernel/fork.c:1520
copy_mm kernel/fork.c:1569 [inline]
copy_process+0x3c95/0x7080 kernel/fork.c:2234
kernel_clone+0xe7/0xab0 kernel/fork.c:2649
__do_sys_clone+0xba/0x100 kernel/fork.c:2783
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 4090:

kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:45
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
kasan_slab_free include/linux/kasan.h:200 [inline]
slab_free_hook mm/slub.c:1727 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
slab_free mm/slub.c:3507 [inline]
kmem_cache_free+0xdd/0x5a0 mm/slub.c:3524

__vma_adjust+0x9ae/0x1910 mm/mmap.c:889
vma_merge+0x590/0x870 mm/mmap.c:1123

userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
__fput+0x277/0x9d0 fs/file_table.c:317
task_work_run+0xdd/0x1a0 kernel/task_work.c:177

get_signal+0x1c5/0x2600 kernel/signal.c:2634
arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff8880781dfe58

which belongs to the cache vm_area_struct of size 152

The buggy address is located 32 bytes inside of
152-byte region [ffff8880781dfe58, ffff8880781dfef0)

The buggy address belongs to the physical page:

page:ffffea0001e077c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x781df
memcg:ffff88801e8b2f01

flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)

raw: 00fff00000000200 ffffea0000973500 dead000000000007 ffff888140006b40
raw: 0000000000000000 0000000000120012 00000001ffffffff ffff88801e8b2f01

page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3812, tgid 3812 (sed), ts 62101588097, free_ts 62100288733

prep_new_page mm/page_alloc.c:2460 [inline]
get_page_from_freelist+0xa64/0x3d10 mm/page_alloc.c:4279
__alloc_pages+0x1c7/0x510 mm/page_alloc.c:5500
alloc_pages+0x1aa/0x310 mm/mempolicy.c:2279
alloc_slab_page mm/slub.c:1797 [inline]
allocate_slab+0x26c/0x3c0 mm/slub.c:1942
new_slab mm/slub.c:2002 [inline]
___slab_alloc+0x985/0xd90 mm/slub.c:3002
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
slab_alloc_node mm/slub.c:3180 [inline]
slab_alloc mm/slub.c:3222 [inline]
__kmem_cache_alloc_lru mm/slub.c:3229 [inline]
kmem_cache_alloc+0x360/0x3b0 mm/slub.c:3239

vm_area_alloc+0x1c/0xf0 kernel/fork.c:458
__install_special_mapping+0x2e/0x3a0 mm/mmap.c:3489
map_vdso+0x131/0x390 arch/x86/entry/vdso/vma.c:268
load_elf_binary+0x206e/0x4ec0 fs/binfmt_elf.c:1287

search_binary_handler fs/exec.c:1728 [inline]
exec_binprm fs/exec.c:1769 [inline]
bprm_execve fs/exec.c:1838 [inline]
bprm_execve+0x7ef/0x1970 fs/exec.c:1800
do_execveat_common+0x724/0x890 fs/exec.c:1943
do_execve fs/exec.c:2017 [inline]
__do_sys_execve fs/exec.c:2093 [inline]
__se_sys_execve fs/exec.c:2088 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1375 [inline]
free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1425
free_unref_page_prepare mm/page_alloc.c:3311 [inline]
free_unref_page_list+0x184/0x1530 mm/page_alloc.c:3475
release_pages+0xff1/0x2290 mm/swap.c:980
tlb_batch_pages_flush+0xa8/0x1a0 mm/mmu_gather.c:58
tlb_flush_mmu_free mm/mmu_gather.c:255 [inline]
tlb_flush_mmu mm/mmu_gather.c:262 [inline]
tlb_finish_mmu+0x147/0x7e0 mm/mmu_gather.c:353

exit_mmap+0x217/0x750 mm/mmap.c:3209

__mmput+0x128/0x4c0 kernel/fork.c:1180
mmput+0x5c/0x70 kernel/fork.c:1201
exec_mmap fs/exec.c:1038 [inline]
begin_new_exec+0xfbd/0x2e50 fs/exec.c:1297
load_elf_binary+0x15a3/0x4ec0 fs/binfmt_elf.c:1002
search_binary_handler fs/exec.c:1728 [inline]
exec_binprm fs/exec.c:1769 [inline]
bprm_execve fs/exec.c:1838 [inline]
bprm_execve+0x7ef/0x1970 fs/exec.c:1800
do_execveat_common+0x724/0x890 fs/exec.c:1943
do_execve fs/exec.c:2017 [inline]
__do_sys_execve fs/exec.c:2093 [inline]
__se_sys_execve fs/exec.c:2088 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:

ffff8880781dfd00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
ffff8880781dfd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880781dfe00: 00 00 00 fc fc fc fc fc fc fc fc fa fb fb fb fb
^
ffff8880781dfe80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
ffff8880781dff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit: 6d0c8068 Add linux-next specific files for 20220610
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13e7c01bf00000

kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=68771c0e74f7bb7804e5
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1679062ff00000

[Hillf Danton]

On Mon, 13 Jun 2022 05:47:08 -0700

v1, See if it is due to trying again without validating pointers.
v2, Add handling of error in userfaultfd_release().

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 6d0c80680317

--- y/mm/mmap.c
+++ m/mm/mmap.c
@@ -674,6 +674,7 @@ int __vma_adjust(struct vm_area_struct *
int remove_next = 0;
MA_STATE(mas, &mm->mm_mt, 0, 0);
struct vm_area_struct *exporter = NULL, *importer = NULL;
+ bool valid_ptr = true;

if (next && !insert) {
if (end >= next->vm_end) {
@@ -760,6 +761,8 @@ again:
vma_adjust_trans_huge(orig_vma, start, end, adjust_next);

if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+ if (!valid_ptr)
+ return -ENOMEM;
if (exporter && exporter->anon_vma)
unlink_anon_vmas(importer);
return -ENOMEM;
@@ -915,6 +918,7 @@ again:
mas_reset(&mas);
remove_next = 1;
end = next->vm_end;
+ valid_ptr = false;
goto again;
}
}

--- y/fs/userfaultfd.c
+++ x/fs/userfaultfd.c
@@ -893,7 +893,7 @@ static int userfaultfd_release(struct in
if (prev)
vma = prev;
else
- prev = vma;
+ continue;
vma->vm_flags = new_flags;
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+68771c...@syzkaller.appspotmail.com

Tested on:

commit: 6d0c8068 Add linux-next specific files for 20220610
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

console output: https://syzkaller.appspot.com/x/log.txt?x=113754dff00000

kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=68771c0e74f7bb7804e5
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=11e906dff00000

Note: testing is done by a robot and is best-effort only.

[Liam Howlett]

* syzbot <syzbot+68771c...@syzkaller.appspotmail.com> [220612 18:08]:

Thank you. This is a valid issue and I have sent a fix [1].

1. https://lore.kernel.org/linux-mm/20220615164150.652...@oracle.com/

Regards,
Liam