On Thu 21-01-16 10:46:00, Ross Zwisler wrote:
> 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 <ross.zwisler@xxxxxxxxxxxxxxx>
> Reported-by: Jan Kara <jack@xxxxxxx>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/dax.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0db21ea..cee9e1b 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;
> @@ -582,6 +583,7 @@ 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;
>
> repeat:
> @@ -1018,6 +1020,7 @@ 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)
> --
> 2.5.0
>
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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