diff options
authorRoss Zwisler <>2016-01-22 15:10:59 -0800
committerLinus Torvalds <>2016-01-22 17:02:18 -0800
commiteab95db69d334745d3034072f4a7204084136c88 (patch)
parent5eb88dca9ce4546bdfca6e5defcd50fbe8ea8411 (diff)
dax: never rely on bh.b_dev being set by get_block()
Previously in DAX we assumed that calls to get_block() would set bh.b_bdev, and we would then use that value even in error cases for debugging. This caused a NULL pointer dereference in __dax_dbg() which was fixed by a previous commit, but that commit only changed the one place where we were hitting an error. Instead, update dax.c so that we always initialize bh.b_bdev as best we can based on the information that DAX has. get_block() may or may not update to a new value, but this at least lets us get something helpful from bh.b_bdev for error messages and not have to worry about whether it was set by get_block() or not. Signed-off-by: Ross Zwisler <> Reported-by: Jan Kara <> Reviewed-by: Jan Kara <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c
index d5f6aca5a4d7..206650f82762 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -246,6 +246,7 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
loff_t end = pos + iov_iter_count(iter);
memset(&bh, 0, sizeof(bh));
+ bh.b_bdev = inode->i_sb->s_bdev;
if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
struct address_space *mapping = inode->i_mapping;
@@ -607,6 +608,7 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
memset(&bh, 0, sizeof(bh));
block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
+ bh.b_bdev = inode->i_sb->s_bdev;
bh.b_size = PAGE_SIZE;
@@ -1078,6 +1080,7 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
BUG_ON((offset + length) > PAGE_CACHE_SIZE);
memset(&bh, 0, sizeof(bh));
+ bh.b_bdev = inode->i_sb->s_bdev;
bh.b_size = PAGE_CACHE_SIZE;
err = get_block(inode, index, &bh, 0);
if (err < 0)