PM: hibernate: Get block device exclusively when do swsusp_check

PATCH In review Ye Bin 2 participants 8 messages Oct 13, 2021 – Oct 21, 2021

Subsystems (2)

Suspend to RAM Hibernation

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Ye Bin

author

2021-10-13 12:06 UTC #0 lore raw

PATCH 1/1 PM: hibernate: Get block device exclusively when do swsusp_check

We got follow issue:

[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:

We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception

The sequence of issue is as follows:
Thread1 Thread2
mount /dev/sda /home/test
get s_mmp_bh --> has mapped flag start kmmpd thread

				echo "/dev/sda" > /sys/power/resume
				  resume_store
				    software_resume
				      swsusp_check
				        set_blocksize
					  truncate_inode_pages_range
					    truncate_cleanup_page
					      block_invalidatepage
					        discard_buffer --> clean mapped flag
write_mmp_block
  submit_bh
    submit_bh_wbc
      BUG_ON(!buffer_mapped(bh)) --> trigger bug_on

To solve this issue, get block device exclusively when do swsusp_check.

Signed-off-by Ye Bin <[email protected]>

---
 kernel/power/swap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

kernel/power/swap.c +3 -2

index 9ec418955556..26c0bd2a50da 100644
@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
 int swsusp_check(void)
 {
 	int error;
+	void *holder;
 
 	hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-					    FMODE_READ, NULL);
+					    FMODE_READ | FMODE_EXCL, &holder);
 	if (!IS_ERR(hib_resume_bdev)) {
 		set_blocksize(hib_resume_bdev, PAGE_SIZE);
 		clear_page(swsusp_header);

@@ -1545,7 +1546,7 @@ int swsusp_check(void)
 
 put:
 		if (error)
-			blkdev_put(hib_resume_bdev, FMODE_READ);
+			blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
 		else
 			pr_debug("Image signature found, resuming\n");
 	} else {

Signature · 1 line

2.31.1

Rafael J. Wysocki

maintainer

2021-10-21 11:01 UTC #3 lore raw

In reply to Ye Bin

Quoted 47 lines · Ye Bin

We got follow issue:

[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:

We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception

The sequence of issue is as follows:
Thread1 Thread2
mount /dev/sda /home/test
get s_mmp_bh --> has mapped flag
start kmmpd thread
echo "/dev/sda" > /sys/power/resume
resume_store
software_resume
swsusp_check
set_blocksize
truncate_inode_pages_range
truncate_cleanup_page
block_invalidatepage
discard_buffer --> clean mapped flag
write_mmp_block
submit_bh

Quoted 4 lines

    submit_bh_wbc
      BUG_ON(!buffer_mapped(bh)) --> trigger bug_on
To solve this issue, get block device exclusively when do swsusp_check.

And why exactly is this going to help?

Quoted 11 lines

Signed-off-by Ye Bin <[email protected]>
---
 kernel/power/swap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
kernel/power/swap.c +0 -0
index 9ec418955556..26c0bd2a50da 100644

kernel/power/swap.c int swsusp_read(unsigned int *flags_p) · line 1527

Quoted 8 lines

kernel/power/swap.c +2 -1

@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
 int swsusp_check(void)
 {
        int error;
+       void *holder;
 
        hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-                                           FMODE_READ, NULL);
+                                           FMODE_READ | FMODE_EXCL, &holder);

So you need to explain to me how this works.

Quoted 13 lines

kernel/power/swap.c +1 -2

        if (!IS_ERR(hib_resume_bdev)) {
                set_blocksize(hib_resume_bdev, PAGE_SIZE);
                clear_page(swsusp_header);

@@ -1545,7 +1546,7 @@ int swsusp_check(void)
 
 put:
                if (error)
-                       blkdev_put(hib_resume_bdev, FMODE_READ);
+                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
                else
                        pr_debug("Image signature found, resuming\n");
        } else {
--

yebin

author

2021-10-21 11:38 UTC #4 lore raw

Quoted 50 lines · Rafael J. Wysocki

Quoted 49 lines · Ye Bin

We got follow issue:

[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:

We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception

     submit_bh_wbc
       BUG_ON(!buffer_mapped(bh)) --> trigger bug_on

Quoted 2 lines

Quoted 1 line
To solve this issue, get block device exclusively when do swsusp_check.
And why exactly is this going to help?

If a block device is already mounted, then do resume, it will discard buffer which file system being used. That can cause the file system to crash and may even cause the system to reset abnormally.
If the "/sys/power/resume" sysfs interface is unrestricted, it will provide criminals with a way to attack the system.

Quoted 15 lines

Signed-off-by Ye Bin <[email protected]>

---
  kernel/power/swap.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

kernel/power/swap.c +1 -0

index 9ec418955556..26c0bd2a50da 100644
@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
  int swsusp_check(void)
  {
         int error;
+       void *holder;

Quoted 4 lines

kernel/power/swap.c int swsusp_read(unsigned int *flags_p) · line 1527

Quoted 3 lines

kernel/power/swap.c +1 -1

         hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-                                           FMODE_READ, NULL);
+                                           FMODE_READ | FMODE_EXCL, &holder);

So you need to explain to me how this works.

As we call 'blkdev_get_by_path' in 'mount_bdev' pass mode includes FMODE_EXCL. So if 'swsusp_check' try to get block device with mode includes FMODE_EXCL will failed.

I think if a block device is used as a swap partition, it cannot be mounted at the same time. Conversely, if a block device is already mounted, it cannot be used as a swap partition.

Quoted 16 lines

Quoted 5 lines

kernel/power/swap.c +0 -0

         if (!IS_ERR(hib_resume_bdev)) {
                 set_blocksize(hib_resume_bdev, PAGE_SIZE);
                 clear_page(swsusp_header);

kernel/power/swap.c int swsusp_check(void)

Quoted 9 lines

kernel/power/swap.c +1 -2

@@ -1545,7 +1546,7 @@ int swsusp_check(void)
 
  put:
                 if (error)
-                       blkdev_put(hib_resume_bdev, FMODE_READ);
+                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
                 else
                         pr_debug("Image signature found, resuming\n");
         } else {
--

Rafael J. Wysocki

maintainer

2021-10-21 13:27 UTC #5 lore raw

Quoted 54 lines · yebin

Quoted 50 lines · Rafael J. Wysocki

Quoted 49 lines · Ye Bin

We got follow issue:

[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:

We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception

     submit_bh_wbc
       BUG_ON(!buffer_mapped(bh)) --> trigger bug_on

Quoted 6 lines

Quoted 2 lines
Quoted 1 line
To solve this issue, get block device exclusively when do swsusp_check.
And why exactly is this going to help?
If a block device is already mounted, then do resume, it will discard buffer
which file system being used. That can cause the file system to crash and may even cause the system to reset abnormally.

I see.

Is there a way to indicate in swsusp_check() that the access will be read-only and so it doesn't care whether or not the block device is in use by someone else?

Quoted 27 lines

If the "/sys/power/resume" sysfs interface is unrestricted, it will provide criminals with a way to attack the system.
Quoted 15 lines
Quoted 15 lines
Signed-off-by Ye Bin <[email protected]>
---
  kernel/power/swap.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)
kernel/power/swap.c +1 -0
index 9ec418955556..26c0bd2a50da 100644
@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
  int swsusp_check(void)
  {
         int error;
+       void *holder;
 
Quoted 4 lines
kernel/power/swap.c int swsusp_read(unsigned int *flags_p) · line 1527
Quoted 3 lines
kernel/power/swap.c +1 -1
         hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-                                           FMODE_READ, NULL);
+                                           FMODE_READ | FMODE_EXCL, &holder);
So you need to explain to me how this works.
As we call 'blkdev_get_by_path' in 'mount_bdev' pass mode includes FMODE_EXCL.
So if 'swsusp_check' try to get block device with mode includes FMODE_EXCL will failed.

Quoted 5 lines

I think if a block device is used as a swap partition, it cannot be mounted at the
same time. Conversely, if a block device is already mounted, it cannot be used as
a swap partition.

Well, what if a hibernation image is located in a swap file? This is one of the cases that need to be supported.

Quoted 17 lines

Quoted 16 lines

Quoted 5 lines

kernel/power/swap.c +0 -0

         if (!IS_ERR(hib_resume_bdev)) {
                 set_blocksize(hib_resume_bdev, PAGE_SIZE);
                 clear_page(swsusp_header);

kernel/power/swap.c int swsusp_check(void)

Quoted 9 lines

kernel/power/swap.c +1 -2

@@ -1545,7 +1546,7 @@ int swsusp_check(void)
 
  put:
                 if (error)
-                       blkdev_put(hib_resume_bdev, FMODE_READ);
+                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
                 else
                         pr_debug("Image signature found, resuming\n");
         } else {
--

yebin

author

2021-10-21 14:38 UTC #6 lore raw

Quoted 60 lines · Rafael J. Wysocki

Quoted 53 lines · yebin
Quoted 50 lines · Rafael J. Wysocki
Quoted 49 lines · Ye Bin
We got follow issue:
[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:
We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception
The sequence of issue is as follows:
Thread1 Thread2
mount /dev/sda /home/test
get s_mmp_bh --> has mapped flag
start kmmpd thread
echo "/dev/sda" > /sys/power/resume
resume_store
software_resume
swsusp_check
set_blocksize
truncate_inode_pages_range
truncate_cleanup_page
block_invalidatepage
discard_buffer --> clean mapped flag
write_mmp_block
    submit_bh
      submit_bh_wbc
        BUG_ON(!buffer_mapped(bh)) --> trigger bug_on
Quoted 6 lines
Quoted 2 lines
Quoted 1 line
To solve this issue, get block device exclusively when do swsusp_check.
And why exactly is this going to help?
If a block device is already mounted, then do resume, it will discard buffer
which file system being used. That can cause the file system to crash and may even cause the system to reset abnormally.

Quoted 5 lines

I see.
Is there a way to indicate in swsusp_check() that the access will be read-only and so it doesn't care whether or not the block device is in use by someone else?

The root reason is that call 'set_blocksize' in 'swsusp_check' which maybe invalidate block device's page.
Moreover, the file system and swap partition share storage space, which will lead to data confusion.

Quoted 27 lines

Quoted 27 lines
If the "/sys/power/resume" sysfs interface is unrestricted, it will provide criminals with a way to attack the system.
Quoted 15 lines
Quoted 15 lines
Signed-off-by Ye Bin <[email protected]>
---
   kernel/power/swap.c | 5 +++--
   1 file changed, 3 insertions(+), 2 deletions(-)
kernel/power/swap.c +1 -0
index 9ec418955556..26c0bd2a50da 100644
@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
   int swsusp_check(void)
   {
          int error;
+       void *holder;
 
Quoted 4 lines
kernel/power/swap.c int swsusp_read(unsigned int *flags_p) · line 1527
Quoted 3 lines
kernel/power/swap.c +1 -1
          hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-                                           FMODE_READ, NULL);
+                                           FMODE_READ | FMODE_EXCL, &holder);
So you need to explain to me how this works.
As we call 'blkdev_get_by_path' in 'mount_bdev' pass mode includes FMODE_EXCL.
So if 'swsusp_check' try to get block device with mode includes FMODE_EXCL will failed.

Quoted 7 lines

Quoted 5 lines
I think if a block device is used as a swap partition, it cannot be mounted at the
same time. Conversely, if a block device is already mounted, it cannot be used as
a swap partition.
Well, what if a hibernation image is located in a swap file? This is one of the cases that need to be supported.

I don't know much about this, but I think the process can call swsusp_check, the hibernation image must be loaded into the block device.

I refer to the process of swapon. If the swap partition is a block device, it is also opened exclusively.
swapon
claim_swapfile
static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)

{
        int error;

        if (S_ISBLK(inode->i_mode)) {    -->If a block device is 
specified, it is also opened exclusively here.
                p->bdev = blkdev_get_by_dev(inode->i_rdev,
                                   FMODE_READ | FMODE_WRITE | 
FMODE_EXCL, p);
                if (IS_ERR(p->bdev)) {
                        error = PTR_ERR(p->bdev);
                        p->bdev = NULL;
                        return error;
                }
                p->old_block_size = block_size(p->bdev);
                error = set_blocksize(p->bdev, PAGE_SIZE);
                if (error < 0)
                        return error;
                /*
                 * Zoned block devices contain zones that have a sequential
                 * write only restriction.  Hence zoned block devices 
are not
                 * suitable for swapping.  Disallow them here.
                 */
                if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
                        return -EINVAL;
                p->flags |= SWP_BLKDEV;
        } else if (S_ISREG(inode->i_mode)) {
                p->bdev = inode->i_sb->s_bdev;
        }

        return 0;
}

Quoted 17 lines

Quoted 5 lines

kernel/power/swap.c +0 -0

          if (!IS_ERR(hib_resume_bdev)) {
                  set_blocksize(hib_resume_bdev, PAGE_SIZE);
                  clear_page(swsusp_header);

@@ -1545,7 +1546,7 @@ int swsusp_check(void)

Quoted 10 lines

kernel/power/swap.c int swsusp_check(void)

Quoted 8 lines

kernel/power/swap.c +1 -2

   put:
                  if (error)
-                       blkdev_put(hib_resume_bdev, FMODE_READ);
+                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
                  else
                          pr_debug("Image signature found, resuming\n");
          } else {
--

Rafael J. Wysocki

maintainer

2021-10-21 17:17 UTC #7 lore raw

Quoted 64 lines · yebin

Quoted 60 lines · Rafael J. Wysocki
Quoted 59 lines · yebin
Quoted 50 lines · Rafael J. Wysocki
Quoted 49 lines · Ye Bin
We got follow issue:
[   89.266592] ------------[ cut here ]------------
[   89.267427] kernel BUG at fs/buffer.c:3020!
[   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
[   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
[   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
[   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
[   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
[   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
[   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
[   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
[   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
[   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
[   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
[   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   89.290368] Call Trace:
[   89.290842]  write_mmp_block+0x2ca/0x510
[   89.292218]  kmmpd+0x433/0x9a0
[   89.294902]  kthread+0x2dd/0x3e0
[   89.296268]  ret_from_fork+0x22/0x30
[   89.296906] Modules linked in:
We can reproduce this issue as follow:
1. mkfs.ext4 -O mmp /dev/sda -b 1024
2. mount /dev/sda /home/test
3. echo "/dev/sda" > /sys/power/resume
4. wait a moment we will get exception
The sequence of issue is as follows:
Thread1 Thread2
mount /dev/sda /home/test
get s_mmp_bh --> has mapped flag
start kmmpd thread
echo "/dev/sda" > /sys/power/resume
resume_store
software_resume
swsusp_check
set_blocksize
truncate_inode_pages_range
truncate_cleanup_page
block_invalidatepage
discard_buffer --> clean mapped flag
write_mmp_block
    submit_bh
      submit_bh_wbc
        BUG_ON(!buffer_mapped(bh)) --> trigger bug_on
Quoted 2 lines
Quoted 1 line
To solve this issue, get block device exclusively when do swsusp_check.
And why exactly is this going to help?
If a block device is already mounted, then do resume, it will discard buffer
which file system being used. That can cause the file system to crash and may even cause the system to reset abnormally.

Quoted 8 lines

Quoted 5 lines
I see.
Is there a way to indicate in swsusp_check() that the access will be read-only and so it doesn't care whether or not the block device is in use by someone else?
The root reason is that call 'set_blocksize' in 'swsusp_check' which maybe invalidate
block device's page.

I see.

Quoted 35 lines

Moreover, the file system and swap partition share storage space, which will lead to
data confusion.
Quoted 32 lines
Quoted 32 lines
If the "/sys/power/resume" sysfs interface is unrestricted, it will provide criminals with a way to attack the system.
Quoted 15 lines
Quoted 15 lines
Signed-off-by Ye Bin <[email protected]>
---
   kernel/power/swap.c | 5 +++--
   1 file changed, 3 insertions(+), 2 deletions(-)
kernel/power/swap.c +1 -0
index 9ec418955556..26c0bd2a50da 100644
@@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
   int swsusp_check(void)
   {
          int error;
+       void *holder;
 
Quoted 4 lines
kernel/power/swap.c int swsusp_read(unsigned int *flags_p) · line 1527
Quoted 3 lines
kernel/power/swap.c +1 -1
          hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-                                           FMODE_READ, NULL);
+                                           FMODE_READ | FMODE_EXCL, &holder);
So you need to explain to me how this works.
As we call 'blkdev_get_by_path' in 'mount_bdev' pass mode includes FMODE_EXCL.
So if 'swsusp_check' try to get block device with mode includes FMODE_EXCL will failed.
I think if a block device is used as a swap partition, it cannot be mounted at the
same time. Conversely, if a block device is already mounted, it cannot be used as
a swap partition.

Quoted 5 lines

Quoted 2 lines
Well, what if a hibernation image is located in a swap file? This is one of the cases that need to be supported.
I don't know much about this, but I think the process can call swsusp_check, the
hibernation image must be loaded into the block device.

Yes, it is invalid to call swsusp_check() without a hibernation image in the target swap partition or swap file if that's what you mean.

However, in the case of a swap file, the image may be there in theory even if the filesystem holding the swap file is mounted.

Quoted 6 lines

I refer to the process of swapon. If the swap partition is a block device, it is also
opened exclusively.
swapon
claim_swapfile

There are two cases, though, the S_ISBLK() one and the S_ISREG() one, and the latter is the swap file case I believe.

Quoted 21 lines

static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)

{
         int error;

         if (S_ISBLK(inode->i_mode)) {    -->If a block device is
specified, it is also opened exclusively here.
                 p->bdev = blkdev_get_by_dev(inode->i_rdev,
                                    FMODE_READ | FMODE_WRITE |
FMODE_EXCL, p);
                 if (IS_ERR(p->bdev)) {
                         error = PTR_ERR(p->bdev);
                         p->bdev = NULL;
                         return error;
                 }
                 p->old_block_size = block_size(p->bdev);
                 error = set_blocksize(p->bdev, PAGE_SIZE);
                 if (error < 0)
                         return error;
                 /*
                  * Zoned block devices contain zones that have a sequential
                  * write only restriction.  Hence zoned block devices

Quoted 8 lines

are not

                  * suitable for swapping.  Disallow them here.
                  */
                 if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
                         return -EINVAL;
                 p->flags |= SWP_BLKDEV;
         } else if (S_ISREG(inode->i_mode)) {
                 p->bdev = inode->i_sb->s_bdev;

Here, it is not exclusive.

Anyway, I think that the change made by the patch should be fine, because it mostly affects restore and I'm not expecting anyone to restore the system from an image in a swap file while the filesystem holding it is mounted.

So I'm going to apply it with some changelog edits.

Thanks!

Quoted 22 lines

         }

         return 0;
}

Quoted 17 lines

Quoted 5 lines

kernel/power/swap.c +0 -0

          if (!IS_ERR(hib_resume_bdev)) {
                  set_blocksize(hib_resume_bdev, PAGE_SIZE);
                  clear_page(swsusp_header);

@@ -1545,7 +1546,7 @@ int swsusp_check(void)

Quoted 10 lines

kernel/power/swap.c int swsusp_check(void)

Quoted 8 lines

kernel/power/swap.c +1 -2

   put:
                  if (error)
-                       blkdev_put(hib_resume_bdev, FMODE_READ);
+                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
                  else
                          pr_debug("Image signature found, resuming\n");
          } else {
--