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Mon, 24 Aug 2020 09:02:40 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9313AB74E; Mon, 24 Aug 2020 09:03:09 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 76A931E1316; Mon, 24 Aug 2020 11:02:39 +0200 (CEST) Date: Mon, 24 Aug 2020 11:02:39 +0200 From: Jan Kara To: Yang Shi Cc: jack@suse.cz, akpm@linux-foundation.org, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: madvise: fix vma user-after-free Message-ID: <20200824090239.GA24877@quack2.suse.cz> References: <20200816141204.162624-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200816141204.162624-1-shy828301@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 7923410097AA4 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005592, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun 16-08-20 07:12:04, Yang Shi wrote: > 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 > RIP: 0033:0x45d4d9 > Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f04f7464c78 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > RAX: ffffffffffffffda RBX: 0000000000020800 RCX: 000000000045d4d9 > RDX: 0000000000000003 RSI: 0000000000600003 RDI: 0000000020000000 > RBP: 000000000118d020 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec > R13: 00007ffc579cce7f R14: 00007f04f74659c0 R15: 000000000118cfec > > Allocated by task 9992: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track mm/kasan/common.c:56 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 > slab_post_alloc_hook mm/slab.h:518 [inline] > slab_alloc mm/slab.c:3312 [inline] > 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: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 > kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 > __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 > __cache_free mm/slab.c:3418 [inline] > 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_sem, but someone else > acquired the mmap_sem and the vma is gone. > > Releasing mmap_sem after accessing vma should fix the problem. > > Fixes: 692fe62433d4c ("mm: Handle MADV_WILLNEED through vfs_fadvise()") > Reported-by: syzbot+b90df26038d1d5d85c97@syzkaller.appspotmail.com > Cc: Jan Kara > Cc: v5.4+ > Signed-off-by: Yang Shi Yeah, good catch! Thanks for fixing this. You can add: Reviewed-by: Jan Kara Honza > --- > mm/madvise.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index dd1d43cf026d..d4aa5f776543 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -289,9 +289,9 @@ static long madvise_willneed(struct vm_area_struct *vma, > */ > *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); > -- > 2.26.2 > -- Jan Kara SUSE Labs, CR