Messages in this thread | | | Subject | Re: [PATCH 1/2] quota: fix null-ptr-deref in ext4_acquire_dquot() | From | "yebin (H)" <> | Date | Mon, 5 Jun 2023 22:08:53 +0800 |
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On 2023/6/5 19:51, Jan Kara wrote: > On Sat 03-06-23 14:14:11, yebin (H) wrote: >> >> On 2023/5/30 17:57, Jan Kara wrote: >>> On Sat 27-05-23 09:40:17, Ye Bin wrote: >>>> Syzbot found the following issue: >>>> Unable to handle kernel paging request at virtual address dfff800000000005 >>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] >>> ... >>>> CPU: 0 PID: 6080 Comm: syz-executor747 Not tainted 6.3.0-rc7-syzkaller-g14f8db1c0f9a #0 >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 >>>> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >>>> pc : ext4_acquire_dquot+0x1d4/0x398 fs/ext4/super.c:6766 >>>> lr : dquot_to_inode fs/ext4/super.c:6740 [inline] >>>> lr : ext4_acquire_dquot+0x1ac/0x398 fs/ext4/super.c:6766 >>> OK, this is bad... >>> >>>> Above issue may happens as follows: >>>> ProcessA ProcessB ProcessC >>>> sys_fsconfig >>>> vfs_fsconfig_locked >>>> reconfigure_super >>>> ext4_remount >>>> dquot_suspend -> suspend all type quota >>>> >>>> sys_fsconfig >>>> vfs_fsconfig_locked >>>> reconfigure_super >>>> ext4_remount >>>> dquot_resume >>>> ret = dquot_load_quota_sb >>>> add_dquot_ref >>>> do_open -> open file O_RDWR >>>> vfs_open >>>> do_dentry_open >>>> get_write_access >>>> atomic_inc_unless_negative(&inode->i_writecount) >>>> ext4_file_open >>>> dquot_file_open >>>> dquot_initialize >>>> __dquot_initialize >>>> dqget >>>> if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) >>>> >>>> __dquot_initialize >>>> __dquot_initialize >>>> dqget >>>> if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) >>>> ext4_acquire_dquot -> Return error >>>> if (ret < 0) >>>> vfs_cleanup_quota_inode >>>> dqopt->files[type] = NULL; >>> But I don't see how this can happen. The code in dquot_load_quota_sb() >>> looks like: >>> >>> error = add_dquot_ref(sb, type); >>> if (error) >>> dquot_disable(sb, type, flags); >>> >>> So if an error happens in add_dquot_ref(), we'll call dquot_disable(). >>> dquot_disable() then does: >>> >>> drop_dquot_ref(sb, cnt); >>> invalidate_dquots(sb, cnt); >>> >>> and invalidate_dquots() waits for reference count of all dquots to drop to >>> 0. Hence if dqget() returned a dquot pointer to ProcessC, then ProcessB >>> should wait until ProcessC drops the dquot reference (hence >>> ext4_acquire_dquot() is done). >>> >>> What am I missing? >>> >>> Honza >> My reproduction condition is: >> mkfs.ext4 -F /dev/sda >> tune2fs -Q usrquota /dev/sda >> >> dquot_disable >> ... >> if ((flags & DQUOT_USAGE_ENABLED && !(flags & >> DQUOT_LIMITS_ENABLED)) >> || (flags & DQUOT_SUSPENDED && flags & (DQUOT_LIMITS_ENABLED | >> DQUOT_USAGE_ENABLED))) >> return -EINVAL; >> ... >> If without enable DQUOT_LIMITS_ENABLED dquot_disable() will just return >> -EINVAL. > Aha, that is the bug! Does attached patch fix your problem? > > Honza Yes , it's works.
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