]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
dax: fix NULL pointer dereference in __dax_dbg()
authorRoss Zwisler <ross.zwisler@linux.intel.com>
Fri, 22 Jan 2016 23:10:31 +0000 (15:10 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 23 Jan 2016 01:02:18 +0000 (17:02 -0800)
commitd4bbe7068b60e9263f08c54e6c2a0166c0f37317
tree2b9f1223bd9742ccffde05d2dfc515231a5afdf5
parent2101ae42899a14fe7caa73114e2161e778328661
dax: fix NULL pointer dereference in __dax_dbg()

In __dax_pmd_fault() we currently assume that get_block() will always
set bh.b_bdev and we unconditionally dereference it in __dax_dbg().

This assumption isn't always true - when called for reads of holes
ext4_dax_mmap_get_block() returns a buffer head where bh->b_bdev is
never set.  I hit this BUG while testing the DAX PMD fault path.

Instead, initialize bh.b_bdev before passing bh into get_block().  It is
possible that the filesystem's get_block() will update bh.b_bdev, and
this is fine - we just want to initialize bh.b_bdev to something
reasonable so that the calls to __dax_dbg() work and print something
useful.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/dax.c