2021-07-12 12:58:20

by David Howells

Subject: [PATCH 2/3] afs: check function return

From: Tom Rix <[email protected]>

Static analysis reports this problem

write.c:773:29: warning: Assigned value is garbage or undefined
mapping->writeback_index = next;
^ ~~~~
The call to afs_writepages_region() can return without setting
next. So check the function return before using next.

Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
Signed-off-by: Tom Rix <[email protected]>
Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---

fs/afs/write.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 3104b62c2082..2794147f82ff 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
mapping->writeback_index = next / PAGE_SIZE;
} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
- if (wbc->nr_to_write > 0)
+ if (wbc->nr_to_write > 0 && ret == 0)
mapping->writeback_index = next;
} else {
ret = afs_writepages_region(mapping, wbc,

2021-07-12 14:22:47

by Marc Dionne

Subject: Re: [PATCH 2/3] afs: check function return

On Mon, Jul 12, 2021 at 9:57 AM David Howells <[email protected]> wrote:
>
> From: Tom Rix <[email protected]>
>
> Static analysis reports this problem
>
> write.c:773:29: warning: Assigned value is garbage or undefined
> mapping->writeback_index = next;
> ^ ~~~~
> The call to afs_writepages_region() can return without setting
> next. So check the function return before using next.
>
> Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
> Signed-off-by: Tom Rix <[email protected]>
> Signed-off-by: David Howells <[email protected]>
> Link: https://lore.kernel.org/r/[email protected]
> ---
>
> fs/afs/write.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/afs/write.c b/fs/afs/write.c
> index 3104b62c2082..2794147f82ff 100644
> --- a/fs/afs/write.c
> +++ b/fs/afs/write.c
> @@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
> mapping->writeback_index = next / PAGE_SIZE;

Isn't there the same issue with the use of next here.

> } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
> ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
> - if (wbc->nr_to_write > 0)
> + if (wbc->nr_to_write > 0 && ret == 0)
> mapping->writeback_index = next;

Unrelated to this patch, but since next is a byte offset, should this
also divide by PAGE_SIZE as above.

> } else {
> ret = afs_writepages_region(mapping, wbc,
>
>

Marc

2021-07-12 15:23:05

by David Howells

Subject: Re: [PATCH 2/3] afs: check function return

Marc Dionne <[email protected]> wrote:

> > @@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
> > mapping->writeback_index = next / PAGE_SIZE;
>
> Isn't there the same issue with the use of next here.

Good point.

> > mapping->writeback_index = next;
>
> Unrelated to this patch, but since next is a byte offset, should this
> also divide by PAGE_SIZE as above.

Also a good point. I'll whip up a separate patch for that.

David