From: "Darrick J. Wong" djwong@kernel.org
commit f8d92a66e810acbef6ddbc0bd0cbd9b117ce8acd upstream.
While I was running with KASAN and lockdep enabled, I stumbled upon an KASAN report about a UAF to a freed CIL checkpoint. Looking at the comment for xfs_log_item_in_current_chkpt, it seems pretty obvious to me that the original patch to xfs_defer_finish_noroll should have done something to lock the CIL to prevent it from switching the CIL contexts while the predicate runs.
For upper level code that needs to know if a given log item is new enough not to need relogging, add a new wrapper that takes the CIL context lock long enough to sample the current CIL context. This is kind of racy in that the CIL can switch the contexts immediately after sampling, but that's ok because the consequence is that the defer ops code is a little slow to relog items.
================================================================== BUG: KASAN: use-after-free in xfs_log_item_in_current_chkpt+0x139/0x160 [xfs] Read of size 8 at addr ffff88804ea5f608 by task fsstress/527999
CPU: 1 PID: 527999 Comm: fsstress Tainted: G D 5.16.0-rc4-xfsx #rc4 Call Trace: <TASK> dump_stack_lvl+0x45/0x59 print_address_description.constprop.0+0x1f/0x140 kasan_report.cold+0x83/0xdf xfs_log_item_in_current_chkpt+0x139/0x160 xfs_defer_finish_noroll+0x3bb/0x1e30 __xfs_trans_commit+0x6c8/0xcf0 xfs_reflink_remap_extent+0x66f/0x10e0 xfs_reflink_remap_blocks+0x2dd/0xa90 xfs_file_remap_range+0x27b/0xc30 vfs_dedupe_file_range_one+0x368/0x420 vfs_dedupe_file_range+0x37c/0x5d0 do_vfs_ioctl+0x308/0x1260 __x64_sys_ioctl+0xa1/0x170 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f2c71a2950b Code: 0f 1e fa 48 8b 05 85 39 0d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 55 39 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe8c0e03c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00005600862a8740 RCX: 00007f2c71a2950b RDX: 00005600862a7be0 RSI: 00000000c0189436 RDI: 0000000000000004 RBP: 000000000000000b R08: 0000000000000027 R09: 0000000000000003 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000005a R13: 00005600862804a8 R14: 0000000000016000 R15: 00005600862a8a20 </TASK>
Allocated by task 464064: kasan_save_stack+0x1e/0x50 __kasan_kmalloc+0x81/0xa0 kmem_alloc+0xcd/0x2c0 [xfs] xlog_cil_ctx_alloc+0x17/0x1e0 [xfs] xlog_cil_push_work+0x141/0x13d0 [xfs] process_one_work+0x7f6/0x1380 worker_thread+0x59d/0x1040 kthread+0x3b0/0x490 ret_from_fork+0x1f/0x30
Freed by task 51: kasan_save_stack+0x1e/0x50 kasan_set_track+0x21/0x30 kasan_set_free_info+0x20/0x30 __kasan_slab_free+0xed/0x130 slab_free_freelist_hook+0x7f/0x160 kfree+0xde/0x340 xlog_cil_committed+0xbfd/0xfe0 [xfs] xlog_cil_process_committed+0x103/0x1c0 [xfs] xlog_state_do_callback+0x45d/0xbd0 [xfs] xlog_ioend_work+0x116/0x1c0 [xfs] process_one_work+0x7f6/0x1380 worker_thread+0x59d/0x1040 kthread+0x3b0/0x490 ret_from_fork+0x1f/0x30
Last potentially related work creation: kasan_save_stack+0x1e/0x50 __kasan_record_aux_stack+0xb7/0xc0 insert_work+0x48/0x2e0 __queue_work+0x4e7/0xda0 queue_work_on+0x69/0x80 xlog_cil_push_now.isra.0+0x16b/0x210 [xfs] xlog_cil_force_seq+0x1b7/0x850 [xfs] xfs_log_force_seq+0x1c7/0x670 [xfs] xfs_file_fsync+0x7c1/0xa60 [xfs] __x64_sys_fsync+0x52/0x80 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae
The buggy address belongs to the object at ffff88804ea5f600 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 8 bytes inside of 256-byte region [ffff88804ea5f600, ffff88804ea5f700) The buggy address belongs to the page: page:ffffea00013a9780 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88804ea5ea00 pfn:0x4ea5e head:ffffea00013a9780 order:1 compound_mapcount:0 flags: 0x4fff80000010200(slab|head|node=1|zone=1|lastcpupid=0xfff) raw: 04fff80000010200 ffffea0001245908 ffffea00011bd388 ffff888004c42b40 raw: ffff88804ea5ea00 0000000000100009 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88804ea5f500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88804ea5f580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804ea5f600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff88804ea5f680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88804ea5f700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================
Fixes: 4e919af7827a ("xfs: periodically relog deferred intent items") Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Dave Chinner dchinner@redhat.com Signed-off-by: Amir Goldstein amir73il@gmail.com Acked-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/xfs/xfs_log_cil.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -1179,9 +1179,9 @@ out_shutdown: */ bool xfs_log_item_in_current_chkpt( - struct xfs_log_item *lip) + struct xfs_log_item *lip) { - struct xfs_cil_ctx *ctx = lip->li_mountp->m_log->l_cilp->xc_ctx; + struct xfs_cil *cil = lip->li_mountp->m_log->l_cilp;
if (list_empty(&lip->li_cil)) return false; @@ -1191,7 +1191,7 @@ xfs_log_item_in_current_chkpt( * first checkpoint it is written to. Hence if it is different to the * current sequence, we're in a new checkpoint. */ - return lip->li_seq == ctx->sequence; + return lip->li_seq == READ_ONCE(cil->xc_current_sequence); }
/*