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Re: [dm-devel] [PATCH] dm-bufio: adjust the reserved buffer for dm-verify-target.





On 2018年08月08日 13:25, Greg KH wrote:
On Wed, Aug 08, 2018 at 01:07:03PM +0800, xiao jin wrote:
We hit the BUG() report at include/linux/scatterlist.h:144!
The callback is as bellow:
   => verity_work
   => verity_hash_for_block
   => verity_verify_level
   => verity_hash
   => verity_hash_update
   => sg_init_one
   => sg_set_buf

More debug shows the root cause. When creating dufio client it
uses the __vmalloc() to allocate the buffer data for the reserved
dm_buffer. The buffer that allocated by the __vmalloc() is invalid
according to the __virt_addr_valid().

Mostly the reserved dm_buffer is not touched. But occasionally
it might fail to allocate the dm_buffer data when we try to
allocate in the __alloc_buffer_wait_no_callback(). Then it has
to take the reserved dm_buffer for usage. Finally it reports the
BUG() as virt_addr_valid() detects the buffer data address is invalid.

The patch is to adjust the reserved buffer for dm-verity-target. We
allocated two dm_buffers into the reserved buffers list when creating
the buffer interface. The first dm_buffer in the reserved buffer list
is allocated by the __vmalloc(), it's not used after that. The second
dm_buffer in the reserved buffer list is allocated by the
__get_free_pages() which can be consumed after that.

Signed-off-by: xiao jin <jin xiao intel com>
---
  drivers/md/dm-bufio.c         | 4 ++--
  drivers/md/dm-verity-target.c | 2 +-
  2 files changed, 3 insertions(+), 3 deletions(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
     https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>
Thanks, I will resend to review without the stable mail list.


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