From: Yang Shi <shy828301@xxxxxxxxx>
commit 7867fd7cc44e63c6673cd0f8fea155456d34d0de upstream.
The syzbot reported the below use-after-free:
BUG: KASAN: use-after-free in madvise_willneed mm/madvise.c:293 [inline]
BUG: KASAN: use-after-free in madvise_vma mm/madvise.c:942 [inline]
BUG: KASAN: use-after-free in do_madvise.part.0+0x1c8b/0x1cf0 mm/madvise.c:1145
Read of size 8 at addr ffff8880a6163eb0 by task syz-executor.0/9996
CPU: 0 PID: 9996 Comm: syz-executor.0 Not tainted 5.9.0-rc1-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+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
madvise_willneed mm/madvise.c:293 [inline]
madvise_vma mm/madvise.c:942 [inline]
do_madvise.part.0+0x1c8b/0x1cf0 mm/madvise.c:1145
do_madvise mm/madvise.c:1169 [inline]
__do_sys_madvise mm/madvise.c:1171 [inline]
__se_sys_madvise mm/madvise.c:1169 [inline]
__x64_sys_madvise+0xd9/0x110 mm/madvise.c:1169
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Allocated by task 9992:
kmem_cache_alloc+0x138/0x3a0 mm/slab.c:3482
vm_area_alloc+0x1c/0x110 kernel/fork.c:347
mmap_region+0x8e5/0x1780 mm/mmap.c:1743
do_mmap+0xcf9/0x11d0 mm/mmap.c:1545
vm_mmap_pgoff+0x195/0x200 mm/util.c:506
ksys_mmap_pgoff+0x43a/0x560 mm/mmap.c:1596
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 9992:
kmem_cache_free.part.0+0x67/0x1f0 mm/slab.c:3693
remove_vma+0x132/0x170 mm/mmap.c:184
remove_vma_list mm/mmap.c:2613 [inline]
__do_munmap+0x743/0x1170 mm/mmap.c:2869
do_munmap mm/mmap.c:2877 [inline]
mmap_region+0x257/0x1780 mm/mmap.c:1716
do_mmap+0xcf9/0x11d0 mm/mmap.c:1545
vm_mmap_pgoff+0x195/0x200 mm/util.c:506
ksys_mmap_pgoff+0x43a/0x560 mm/mmap.c:1596
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
It is because vma is accessed after releasing mmap_lock, but someone
else acquired the mmap_lock and the vma is gone.
Releasing mmap_lock after accessing vma should fix the problem.
Fixes: 692fe62433d4c ("mm: Handle MADV_WILLNEED through vfs_fadvise()")
Reported-by: syzbot+b90df26038d1d5d85c97@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.4+]
Link: https://lkml.kernel.org/r/20200816141204.162624-1-shy828301@xxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/madvise.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -289,9 +289,9 @@ static long madvise_willneed(struct vm_a
*/
*prev = NULL; /* tell sys_madvise we drop mmap_lock */
get_file(file);
- mmap_read_unlock(current->mm);
offset = (loff_t)(start - vma->vm_start)
+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+ mmap_read_unlock(current->mm);
vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
fput(file);
mmap_read_lock(current->mm);
