f4fa8d937e
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.