On 29 March 2017 at 23:08, Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx> > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> > --- > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
