| From fa81ca27ad75d71c9bb71d84598d22fc70cb478a Mon Sep 17 00:00:00 2001 |
| From: Yang Shi <shy828301@gmail.com> |
| Date: Fri, 4 Sep 2020 16:35:55 -0700 |
| Subject: [PATCH] mm: madvise: fix vma user-after-free |
| |
| 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@syzkaller.appspotmail.com |
| Signed-off-by: Yang Shi <shy828301@gmail.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Reviewed-by: Andrew Morton <akpm@linux-foundation.org> |
| Reviewed-by: Jan Kara <jack@suse.cz> |
| Cc: <stable@vger.kernel.org> [5.4+] |
| Link: https://lkml.kernel.org/r/20200816141204.162624-1-shy828301@gmail.com |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/mm/madvise.c b/mm/madvise.c |
| index ae56d0ef337d..9c43c8515cef 100644 |
| --- a/mm/madvise.c |
| +++ b/mm/madvise.c |
| @@ -308,9 +308,9 @@ static long madvise_willneed(struct vm_area_struct *vma, |
| */ |
| *prev = NULL; /* tell sys_madvise we drop mmap_sem */ |
| get_file(file); |
| - up_read(¤t->mm->mmap_sem); |
| offset = (loff_t)(start - vma->vm_start) |
| + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); |
| + up_read(¤t->mm->mmap_sem); |
| vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED); |
| fput(file); |
| down_read(¤t->mm->mmap_sem); |
| -- |
| 2.27.0 |
| |
