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([2a02:908:1252:fb60:be8a:bd56:1f94:86e7]) by smtp.gmail.com with ESMTPSA id o11sm10466764ejd.60.2020.10.12.05.19.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Oct 2020 05:19:47 -0700 (PDT) Reply-To: christian.koenig@amd.com Subject: Re: [patch 3/5] mm: mmap: fix general protection fault in unlink_file_vma() To: Andrew Morton , airlied@redhat.com, chris@chris-wilson.co.uk, daniel@ffwll.ch, jhubbard@nvidia.com, linmiaohe@huawei.com, linux-mm@kvack.org, louhongxiang@huawei.com, mm-commits@vger.kernel.org, sumit.semwal@linaro.org, torvalds@linux-foundation.org, willy@infradead.org References: <20201011061634.E2EVnOdUx%akpm@linux-foundation.org> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <7b38790e-9515-f849-ad70-458d5f081651@gmail.com> Date: Mon, 12 Oct 2020 14:19:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201011061634.E2EVnOdUx%akpm@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Am 11.10.20 um 08:16 schrieb Andrew Morton: > From: Miaohe Lin > Subject: mm: mmap: Fix general protection fault in unlink_file_vma() > > The syzbot reported the below general protection fault: > > general protection fault, probably for non-canonical address > 0xe00eeaee0000003b: 0000 [#1] PREEMPT SMP KASAN > KASAN: maybe wild-memory-access in range > [0x00777770000001d8-0x00777770000001df] > CPU: 1 PID: 10488 Comm: syz-executor721 Not tainted 5.9.0-rc3-syzkaller= #0 > RIP: 0010:unlink_file_vma+0x57/0xb0 mm/mmap.c:164 > Code: 4c 8b a5 a0 00 00 00 4d 85 e4 74 4e e8 92 d7 cd ff 49 8d bc 24 > d8 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c > 02 00 75 3d 4d 8b b4 24 d8 01 00 00 4d 8d 6e 78 4c 89 ef e8 > RSP: 0018:ffffc9000ac0f9b0 EFLAGS: 00010202 > RAX: dffffc0000000000 RBX: ffff88800010ceb0 RCX: ffffffff81592421 > RDX: 000eeeee0000003b RSI: ffffffff81a6736e RDI: 00777770000001d8 > RBP: ffff88800010ceb0 R08: 0000000000000001 R09: ffff88801291a50f > R10: ffffed10025234a1 R11: 0000000000000001 R12: 0077777000000000 > R13: 00007f1eea0da000 R14: 00007f1eea0d9000 R15: 0000000000000000 > FS: 0000000000000000(0000) GS:ffff8880ae700000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f1eea11a9d0 CR3: 000000000007e000 CR4: 00000000001506e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > free_pgtables+0x1b3/0x2f0 mm/memory.c:415 > exit_mmap+0x2c0/0x530 mm/mmap.c:3184 > __mmput+0x122/0x470 kernel/fork.c:1076 > mmput+0x53/0x60 kernel/fork.c:1097 > exit_mm kernel/exit.c:483 [inline] > do_exit+0xa8b/0x29f0 kernel/exit.c:793 > do_group_exit+0x125/0x310 kernel/exit.c:903 > get_signal+0x428/0x1f00 kernel/signal.c:2757 > arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811 > exit_to_user_mode_loop kernel/entry/common.c:136 [inline] > exit_to_user_mode_prepare+0x1ae/0x200 kernel/entry/common.c:167 > syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:242 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > It's because the ->mmap() callback can change vma->vm_file and fput the > original file. But the commit d70cec898324 ("mm: mmap: merge vma after > call_mmap() if possible") failed to catch this case and always fput() t= he > original file, hence add an extra fput(). > > [ Thanks Hillf for pointing this extra fput() out. ] > > Link: https://lkml.kernel.org/r/20200916090733.31427-1-linmiaohe@huawei= .com > Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible= ") > Signed-off-by: Miaohe Lin > Reported-by: syzbot+c5d5a51dcbb558ca0cb5@syzkaller.appspotmail.com > Cc: Christian K=C3=B6nig > Cc: Hongxiang Lou > Cc: Chris Wilson > Cc: Dave Airlie > Cc: Daniel Vetter > Cc: Sumit Semwal > Cc: Matthew Wilcox (Oracle) > Cc: John Hubbard > Signed-off-by: Andrew Morton Reviewed-by: Christian K=C3=B6nig > --- > > mm/mmap.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > --- a/mm/mmap.c~mm-mmap-fix-general-protection-fault-in-unlink_file_vma > +++ a/mm/mmap.c > @@ -1781,7 +1781,11 @@ unsigned long mmap_region(struct file *f > merge =3D vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_= flags, > NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX); > if (merge) { > - fput(file); > + /* ->mmap() can change vma->vm_file and fput the original file. So > + * fput the vma->vm_file here or we would add an extra fput for fi= le > + * and cause general protection fault ultimately. > + */ > + fput(vma->vm_file); > vm_area_free(vma); > vma =3D merge; > /* Update vm_flags and possible addr to pick up the change. We do= n't > _