All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH] writeback: expired dirty inodes can lead to a NULL dereference kernel panic issue in 'move_expired_inodes' function
@ 2022-04-08  7:18 Paran Lee
  2022-04-08  9:25 ` Colin King (gmail)
  2022-04-08 11:25 ` Greg KH
  0 siblings, 2 replies; 5+ messages in thread
From: Paran Lee @ 2022-04-08  7:18 UTC (permalink / raw)
  To: colin.i.king; +Cc: stable, Austin Kim

writeback: expired dirty inodes can lead to a NULL dereference kernel panic issue in 'move_expired_inodes' function

Hello, Colin Ian King.

I am Paran Lee.

While tracing the null dereference kernel panic issue during the stress-ng(stress-ng-proc) test,
I found the inode code block that could cause a null dereference kernel panic.

If this issue is confirmed as a bug that may have occurred in the past, wouldn't it be added to the link below?

@ Bugs found with stress-ng
- https://github.com/ColinIanKing/stress-ng#bugs-found-with-stress-ng

* kernel log

[21881.096120] ICMPv6: process `stress-ng-procf' is using deprecated sysctl (syscall) net.ipv6.neigh.default.base_reachable_time - use net.ipv6.neigh.default.base_reachable_time_ms instead
[22009.051158] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[22009.051167] IP: move_expired_inodes+0x59/0x1a0
[22009.051168] PGD 0 P4D 0
[22009.051170] Oops: 0002 [#1] SMP NOPTI
...
[22009.051221] RIP: 0010:move_expired_inodes+0x59/0x1a0
...
[22009.051257] Call Trace:
[22009.051260]  queue_io+0x66/0x110
[22009.051262]  wb_writeback+0x253/0x300
[22009.051264]  wb_workfn+0xc0/0x400
[22009.051265]  ? wb_workfn+0xc0/0x400
[22009.051268]  ? __switch_to_asm+0x35/0x70
[22009.051272]  process_one_work+0x1de/0x420
[22009.051274]  worker_thread+0x32/0x410
[22009.051276]  kthread+0x121/0x140
[22009.051277]  ? process_one_work+0x420/0x420
[22009.051279]  ? kthread_create_worker_on_cpu+0x70/0x70
[22009.051280]  ret_from_fork+0x1f/0x40
[22009.051282] Code: 04 25 28 00 00 00 48 89 45 d0 31 c0 4c 89 75 c8 c7 45 b0 00 00 00 00 c7 45 b4 00 00 00 00 eb 76 48 8b 3b 48 8b 43 08 83 45 b0 01 <48> 89 47 08 48 89 38 48 8b 45 c0 48 89 58 08 48 89 03 48 8d 43
[22009.051293] RIP: move_expired_inodes+0x59/0x1a0 RSP: ffffa2f68413bcb0

* trace log on crash utility

      KERNEL: vmlinux-4.15.0-166-generic
    DUMPFILE: 202204072123-wb_inode-delaying_queue-list-null-check/dump.202204072123  [PARTIAL DUMP]
        CPUS: 4
        DATE: Fri Apr  8 06:23:30 2022
      UPTIME: 01:35:27
LOAD AVERAGE: 8.30, 8.37, 9.17
       TASKS: 668
    NODENAME: ubuntu1804
     RELEASE: 4.15.0-166-generic
     VERSION: #174-Ubuntu SMP Wed Dec 8 19:07:44 UTC 2021
     MACHINE: x86_64  (2394 Mhz)
      MEMORY: 16 GB
       PANIC: "BUG: unable to handle kernel NULL pointer dereference at 0000000000000008"
         PID: 22864
     COMMAND: "kworker/u8:0"
        TASK: ffff91490b55d880  [THREAD_INFO: ffff91490b55d880]
         CPU: 0
       STATE: TASK_RUNNING (PANIC)

crash> bt
...
 #9 [ffffa2f68413bc00] page_fault at ffffffffae401615
    [exception RIP: move_expired_inodes+89]
    RIP: ffffffffadcb11f9  RSP: ffffa2f68413bcb0  RFLAGS: 00010202
    RAX: 0000000000000000  RBX: ffff9148083af9b8  RCX: ffff91496659a090
    RDX: 000000010052d046  RSI: ffff91496659a080  RDI: 0000000000000000
    RBP: ffffa2f68413bd08   R8: ffff91496676727f   R9: ffff914951111f76
    R10: ffffa2f68413bdf8  R11: 0000000000000334  R12: 0000000000000000
    R13: ffff91496659a070  R14: ffffa2f68413bcc8  R15: ffff91496659a080
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
#10 [ffffa2f68413bd10] queue_io at ffffffffadcb32d6
#11 [ffffa2f68413bd48] wb_writeback at ffffffffadcb77a3
#12 [ffffa2f68413bde8] wb_workfn at ffffffffadcb7eb0
#13 [ffffa2f68413be80] process_one_work at ffffffffadaaa68e
#14 [ffffa2f68413bec8] worker_thread at ffffffffadaaa902
#15 [ffffa2f68413bf08] kthread at ffffffffadab1361
#16 [ffffa2f68413bf50] ret_from_fork at ffffffffae4001ef

crash> dis ffffffffadcb32c6 20
...
0xffffffffadcb32c6 <queue_io+86>:       jg     0xffffffffadcb32e0 <queue_io+112>
0xffffffffadcb32c8 <queue_io+88>:       mov    %rsi,%r14
0xffffffffadcb32cb <queue_io+91>:       mov    %r12,%rsi
0xffffffffadcb32ce <queue_io+94>:       mov    %rdx,%r13
0xffffffffadcb32d1 <queue_io+97>:       callq  0xffffffffadcb11a0 <move_expired_inodes>

crash> dis 0xffffffffadcb11a0
0xffffffffadcb11a0 <move_expired_inodes>:       nopl   0x0(%rax,%rax,1) [FTRACE NOP]
...
0xffffffffadcb11ec <move_expired_inodes+76>:    jmp    0xffffffffadcb1264 <move_expired_inodes+196>
0xffffffffadcb11ee <move_expired_inodes+78>:    mov    (%rbx),%rdi
0xffffffffadcb11f1 <move_expired_inodes+81>:    mov    0x8(%rbx),%rax
0xffffffffadcb11f5 <move_expired_inodes+85>:    addl   $0x1,-0x50(%rbp)
0xffffffffadcb11f9 <move_expired_inodes+89>:    mov    %rax,0x8(%rdi)    <<<<<< Don't you think this is the NULL dereference RIP point of it?
0xffffffffadcb11fd <move_expired_inodes+93>:    mov    %rdi,(%rax)
...
0xffffffffadcb121e <move_expired_inodes+126>:   callq  0xffffffffae3cd460 <_raw_spin_lock>

Have a good day.
Paran Lee.

Signed-off-by: Paran Lee <p4ranlee@gmail.com>
---
 fs/fs-writeback.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 591fe9cf1659..23a7a567e443 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1357,12 +1357,14 @@ static int move_expired_inodes(struct list_head *delaying_queue,
 	LIST_HEAD(tmp);
 	struct list_head *pos, *node;
 	struct super_block *sb = NULL;
-	struct inode *inode;
+	struct inode *inode = NULL;
 	int do_sb_sort = 0;
 	int moved = 0;
 
 	while (!list_empty(delaying_queue)) {
 		inode = wb_inode(delaying_queue->prev);
+		if(!inode)
+			continue;
 		if (inode_dirtied_after(inode, dirtied_before))
 			break;
 		list_move(&inode->i_io_list, &tmp);
@@ -1385,7 +1387,12 @@ static int move_expired_inodes(struct list_head *delaying_queue,
 
 	/* Move inodes from one superblock together */
 	while (!list_empty(&tmp)) {
-		sb = wb_inode(tmp.prev)->i_sb;
+		inode = wb_inode(tmp.prev);
+		if(!inode)
+			continue;
+		sb = inode->i_sb;
+		if(!sb)
+			continue;
 		list_for_each_prev_safe(pos, node, &tmp) {
 			inode = wb_inode(pos);
 			if (inode->i_sb == sb)
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH] writeback: expired dirty inodes can lead to a NULL dereference kernel panic issue in 'move_expired_inodes' function
@ 2022-04-08 12:00 Paran Lee
  2022-04-08 12:15 ` Matthew Wilcox
  0 siblings, 1 reply; 5+ messages in thread
From: Paran Lee @ 2022-04-08 12:00 UTC (permalink / raw)
  To: Jan Kara; +Cc: linux-fsdevel, Nicholas Piggin, Christoph Hellwig, Austin Kim

While tracing the null dereference kernel panic issue 

during the stress-ng(stress-ng-proc) test,

I found the inode code block that could cause 

a null dereference kernel panic. 

BUG: unable to handle kernel NULL pointer dereference at 0000000000000008

inode stack variable not initialized and not check on this code block. 

but find entry in delaying_queue. then, there was something suspicious 

temp inode loop that could cause a kernel panic in below code block.

Signed-off-by: Paran Lee <p4ranlee@gmail.com>
---
 fs/fs-writeback.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 591fe9cf1659..23a7a567e443 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1357,12 +1357,14 @@ static int move_expired_inodes(struct list_head *delaying_queue,
 	LIST_HEAD(tmp);
 	struct list_head *pos, *node;
 	struct super_block *sb = NULL;
-	struct inode *inode;
+	struct inode *inode = NULL;
 	int do_sb_sort = 0;
 	int moved = 0;
 
 	while (!list_empty(delaying_queue)) {
 		inode = wb_inode(delaying_queue->prev);
+		if (!inode)
+			continue;
 		if (inode_dirtied_after(inode, dirtied_before))
 			break;
 		list_move(&inode->i_io_list, &tmp);
@@ -1385,7 +1387,12 @@ static int move_expired_inodes(struct list_head *delaying_queue,
 
 	/* Move inodes from one superblock together */
 	while (!list_empty(&tmp)) {
-		sb = wb_inode(tmp.prev)->i_sb;
+		inode = wb_inode(tmp.prev);
+		if (!inode)
+			continue;
+		sb = inode->i_sb;
+		if (!sb)
+			continue;
 		list_for_each_prev_safe(pos, node, &tmp) {
 			inode = wb_inode(pos);
 			if (inode->i_sb == sb)
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-04-08 12:15 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-04-08  7:18 [PATCH] writeback: expired dirty inodes can lead to a NULL dereference kernel panic issue in 'move_expired_inodes' function Paran Lee
2022-04-08  9:25 ` Colin King (gmail)
2022-04-08 11:25 ` Greg KH
  -- strict thread matches above, loose matches on Subject: below --
2022-04-08 12:00 Paran Lee
2022-04-08 12:15 ` Matthew Wilcox

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.