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SubjectRe: [PATCH RESEND] mm/hugetlb: Don't call region_abort if region_chg fails
On 29 March 2017 at 23:08, Mike Kravetz <mike.kravetz@oracle.com> wrote:
> Changes to hugetlbfs reservation maps is a two step process. The first
> step is a call to region_chg to determine what needs to be changed, and
> prepare that change. This should be followed by a call to call to
> region_add to commit the change, or region_abort to abort the change.
>
> The error path in hugetlb_reserve_pages called region_abort after a
> failed call to region_chg. As a result, the adds_in_progress counter
> in the reservation map is off by 1. This is caught by a VM_BUG_ON
> in resv_map_release when the reservation map is freed.
>
> syzkaller fuzzer found this bug, that resulted in the following:
>
> kernel BUG at mm/hugetlb.c:742!
> Call Trace:
> hugetlbfs_evict_inode+0x7b/0xa0 fs/hugetlbfs/inode.c:493
> evict+0x481/0x920 fs/inode.c:553
> iput_final fs/inode.c:1515 [inline]
> iput+0x62b/0xa20 fs/inode.c:1542
> hugetlb_file_setup+0x593/0x9f0 fs/hugetlbfs/inode.c:1306
> newseg+0x422/0xd30 ipc/shm.c:575
> ipcget_new ipc/util.c:285 [inline]
> ipcget+0x21e/0x580 ipc/util.c:639
> SYSC_shmget ipc/shm.c:673 [inline]
> SyS_shmget+0x158/0x230 ipc/shm.c:657
> entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: resv_map_release+0x265/0x330 mm/hugetlb.c:742
>
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index c7025c1..c65d45c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4233,7 +4233,9 @@ int hugetlb_reserve_pages(struct inode *inode,
> return 0;
> out_err:
> if (!vma || vma->vm_flags & VM_MAYSHARE)
> - region_abort(resv_map, from, to);
> + /* Don't call region_abort if region_chg failed */
> + if (chg >= 0)
> + region_abort(resv_map, from, to);
> if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
> kref_put(&resv_map->refs, resv_map_release);
> return ret;

Hi guys,

I'm running into this on latest linus/master:

kernel BUG at mm/hugetlb.c:742!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 3 PID: 20281 Comm: syz-executor0 Not tainted 4.11.0-rc6 #335
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff880064f30dc0 task.stack: ffff880065b38000
RIP: 0010:resv_map_release+0x1cb/0x270
RSP: 0018:ffff880065b3fc38 EFLAGS: 00010287
RAX: 0000000000010000 RBX: ffff88006b5fe418 RCX: ffffc90001b52000
RDX: 00000000000005de RSI: ffffffff8172026b RDI: ffff88006b5fe410
RBP: ffff880065b3fc78 R08: ffff880065b3f958 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff88006b5fe418 R14: ffff88006b5fe418 R15: ffff88006b5fe418
FS: 00007f21647c5700(0000) GS:ffff88006d100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000460750 CR3: 000000005d123000 CR4: 00000000000006e0
Call Trace:
hugetlbfs_evict_inode+0x80/0xa0
? hugetlbfs_setattr+0x3c0/0x3c0
evict+0x24a/0x620
iput+0x48f/0x8c0
dentry_unlink_inode+0x31f/0x4d0
__dentry_kill+0x292/0x5e0
dput+0x730/0x830
__fput+0x438/0x720
____fput+0x1a/0x20
task_work_run+0xfe/0x180
exit_to_usermode_loop+0x133/0x150
syscall_return_slowpath+0x184/0x1c0
entry_SYSCALL_64_fastpath+0xab/0xad

To reproduce:

mmap(0, 0x2000, 0, 0x40031, 0xffffffffffffffffULL, 0x8000000000000000ULL);

Curiously enough, it's the patch from this thread (i.e. commit
ff8c0c53c47530ffea82c22a0a6df6332b56c957) that introduces it,
according to git bisect. Reverting the commit from linus/master fixes
the problem.

Also found by syzcaller (no fault injections this time).


Vegard

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