diff mbox series

[1/2] virtiofs, dax: Fix smatch warning about loss of info during shift

Message ID 20210506184304.321645-2-vgoyal@redhat.com (mailing list archive)
State New
Headers show
Series virtiofs, dax: Fix couple of smatch warnings | expand

Commit Message

Vivek Goyal May 6, 2021, 6:43 p.m. UTC
Dan reported a smatch warning during potentential loss of info during
left shift if this code is compiled on 32bit systems.

New smatch warnings:
fs/fuse/dax.c:113 fuse_setup_one_mapping() warn: should 'start_idx << 21' be a
+64 bit type?

I ran smatch and found two more instances of similar warning. This patch
fixes all such instances.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/fuse/dax.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Dr. David Alan Gilbert May 6, 2021, 7:07 p.m. UTC | #1
* Vivek Goyal (vgoyal@redhat.com) wrote:
> Dan reported a smatch warning during potentential loss of info during
> left shift if this code is compiled on 32bit systems.
> 
> New smatch warnings:
> fs/fuse/dax.c:113 fuse_setup_one_mapping() warn: should 'start_idx << 21' be a
> +64 bit type?
> 
> I ran smatch and found two more instances of similar warning. This patch
> fixes all such instances.
> 
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  fs/fuse/dax.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
> index ff99ab2a3c43..f06fdad3f7b1 100644
> --- a/fs/fuse/dax.c
> +++ b/fs/fuse/dax.c
> @@ -186,7 +186,7 @@ static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
>  	struct fuse_conn_dax *fcd = fm->fc->dax;
>  	struct fuse_inode *fi = get_fuse_inode(inode);
>  	struct fuse_setupmapping_in inarg;
> -	loff_t offset = start_idx << FUSE_DAX_SHIFT;
> +	loff_t offset = (loff_t)start_idx << FUSE_DAX_SHIFT;

I've not followed the others back, but isn't it easier to change
the start_idx parameter to be a loff_t, since the places it's called
from are poth loff_t pos?

Dave

>  	FUSE_ARGS(args);
>  	ssize_t err;
>  
> @@ -872,7 +872,7 @@ static int dmap_writeback_invalidate(struct inode *inode,
>  				     struct fuse_dax_mapping *dmap)
>  {
>  	int ret;
> -	loff_t start_pos = dmap->itn.start << FUSE_DAX_SHIFT;
> +	loff_t start_pos = (loff_t)dmap->itn.start << FUSE_DAX_SHIFT;
>  	loff_t end_pos = (start_pos + FUSE_DAX_SZ - 1);
>  
>  	ret = filemap_fdatawrite_range(inode->i_mapping, start_pos, end_pos);
> @@ -966,7 +966,7 @@ inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
>  	dmap = inode_lookup_first_dmap(inode);
>  	if (dmap) {
>  		start_idx = dmap->itn.start;
> -		dmap_start = start_idx << FUSE_DAX_SHIFT;
> +		dmap_start = (u64)start_idx << FUSE_DAX_SHIFT;
>  		dmap_end = dmap_start + FUSE_DAX_SZ - 1;
>  	}
>  	up_read(&fi->dax->sem);
> @@ -1118,7 +1118,7 @@ static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
>  {
>  	int ret;
>  	struct fuse_inode *fi = get_fuse_inode(inode);
> -	loff_t dmap_start = start_idx << FUSE_DAX_SHIFT;
> +	loff_t dmap_start = (loff_t)start_idx << FUSE_DAX_SHIFT;
>  	loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1;
>  
>  	down_write(&fi->i_mmap_sem);
> -- 
> 2.25.4
>
Matthew Wilcox (Oracle) May 6, 2021, 7:35 p.m. UTC | #2
On Thu, May 06, 2021 at 08:07:39PM +0100, Dr. David Alan Gilbert wrote:
> > @@ -186,7 +186,7 @@ static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
> >  	struct fuse_conn_dax *fcd = fm->fc->dax;
> >  	struct fuse_inode *fi = get_fuse_inode(inode);
> >  	struct fuse_setupmapping_in inarg;
> > -	loff_t offset = start_idx << FUSE_DAX_SHIFT;
> > +	loff_t offset = (loff_t)start_idx << FUSE_DAX_SHIFT;
> 
> I've not followed the others back, but isn't it easier to change
> the start_idx parameter to be a loff_t, since the places it's called
> from are poth loff_t pos?

But an index isn't a file offset, and shouldn't be typed as such.
Vivek Goyal May 10, 2021, 6:16 p.m. UTC | #3
On Thu, May 06, 2021 at 12:35:17PM -0700, Matthew Wilcox wrote:
> On Thu, May 06, 2021 at 08:07:39PM +0100, Dr. David Alan Gilbert wrote:
> > > @@ -186,7 +186,7 @@ static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
> > >  	struct fuse_conn_dax *fcd = fm->fc->dax;
> > >  	struct fuse_inode *fi = get_fuse_inode(inode);
> > >  	struct fuse_setupmapping_in inarg;
> > > -	loff_t offset = start_idx << FUSE_DAX_SHIFT;
> > > +	loff_t offset = (loff_t)start_idx << FUSE_DAX_SHIFT;
> > 
> > I've not followed the others back, but isn't it easier to change
> > the start_idx parameter to be a loff_t, since the places it's called
> > from are poth loff_t pos?
> 
> But an index isn't a file offset, and shouldn't be typed as such.

Agreed. This is index, so it seems better to not use "loff_t" to
represent it.

Vivek
diff mbox series

Patch

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index ff99ab2a3c43..f06fdad3f7b1 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -186,7 +186,7 @@  static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
 	struct fuse_conn_dax *fcd = fm->fc->dax;
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_setupmapping_in inarg;
-	loff_t offset = start_idx << FUSE_DAX_SHIFT;
+	loff_t offset = (loff_t)start_idx << FUSE_DAX_SHIFT;
 	FUSE_ARGS(args);
 	ssize_t err;
 
@@ -872,7 +872,7 @@  static int dmap_writeback_invalidate(struct inode *inode,
 				     struct fuse_dax_mapping *dmap)
 {
 	int ret;
-	loff_t start_pos = dmap->itn.start << FUSE_DAX_SHIFT;
+	loff_t start_pos = (loff_t)dmap->itn.start << FUSE_DAX_SHIFT;
 	loff_t end_pos = (start_pos + FUSE_DAX_SZ - 1);
 
 	ret = filemap_fdatawrite_range(inode->i_mapping, start_pos, end_pos);
@@ -966,7 +966,7 @@  inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
 	dmap = inode_lookup_first_dmap(inode);
 	if (dmap) {
 		start_idx = dmap->itn.start;
-		dmap_start = start_idx << FUSE_DAX_SHIFT;
+		dmap_start = (u64)start_idx << FUSE_DAX_SHIFT;
 		dmap_end = dmap_start + FUSE_DAX_SZ - 1;
 	}
 	up_read(&fi->dax->sem);
@@ -1118,7 +1118,7 @@  static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
 {
 	int ret;
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	loff_t dmap_start = start_idx << FUSE_DAX_SHIFT;
+	loff_t dmap_start = (loff_t)start_idx << FUSE_DAX_SHIFT;
 	loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1;
 
 	down_write(&fi->i_mmap_sem);