From: Tom Rix <[email protected]>
clang static analysis flags a garbage return
fs/btrfs/reflink.c:611:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
return ret;
^~~~~~~~~~
ret will not be set when olen is 0
When olen is 0, this function does no work.
So initialize ret to 0
Signed-off-by: Tom Rix <[email protected]>
---
fs/btrfs/reflink.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index 040009d1cc31..200a80fcbecb 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -572,7 +572,7 @@ static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 len,
static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
struct inode *dst, u64 dst_loff)
{
- int ret;
+ int ret = 0;
u64 i, tail_len, chunk_count;
struct btrfs_root *root_dst = BTRFS_I(dst)->root;
--
2.18.1
On 5.07.20 г. 17:20 ч., [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> clang static analysis flags a garbage return
>
> fs/btrfs/reflink.c:611:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
> return ret;
> ^~~~~~~~~~
> ret will not be set when olen is 0
> When olen is 0, this function does no work.
>
> So initialize ret to 0
>
> Signed-off-by: Tom Rix <[email protected]>
And I forgot:
Reviewed-by: Nikolay Borisov <[email protected]>
> ---
> fs/btrfs/reflink.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
> index 040009d1cc31..200a80fcbecb 100644
> --- a/fs/btrfs/reflink.c
> +++ b/fs/btrfs/reflink.c
> @@ -572,7 +572,7 @@ static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 len,
> static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> struct inode *dst, u64 dst_loff)
> {
> - int ret;
> + int ret = 0;
> u64 i, tail_len, chunk_count;
> struct btrfs_root *root_dst = BTRFS_I(dst)->root;
>
>
On 5.07.20 г. 17:20 ч., [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> clang static analysis flags a garbage return
>
> fs/btrfs/reflink.c:611:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
> return ret;
> ^~~~~~~~~~
> ret will not be set when olen is 0
> When olen is 0, this function does no work.
>
> So initialize ret to 0
>
> Signed-off-by: Tom Rix <[email protected]>
Patch itself is good however, the bug cannot currently be triggered, due
to the following code in the sole caller (btrfs_remap_file_range):
15 if (ret < 0 || len == 0)
14 goto out_unlock;
13
12 if (remap_flags & REMAP_FILE_DEDUP)
11 ret = btrfs_extent_same(src_inode, off, len,
dst_inode, destoff);
10 else
9 ret = btrfs_clone_files(dst_file, src_file, off,
len, destoff);
i.e len is guaranteed to be non-zero
> ---
> fs/btrfs/reflink.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
> index 040009d1cc31..200a80fcbecb 100644
> --- a/fs/btrfs/reflink.c
> +++ b/fs/btrfs/reflink.c
> @@ -572,7 +572,7 @@ static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 len,
> static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> struct inode *dst, u64 dst_loff)
> {
> - int ret;
> + int ret = 0;
> u64 i, tail_len, chunk_count;
> struct btrfs_root *root_dst = BTRFS_I(dst)->root;
>
>
On Sun, Jul 05, 2020 at 05:48:17PM +0300, Nikolay Borisov wrote:
> On 5.07.20 г. 17:20 ч., [email protected] wrote:
> > From: Tom Rix <[email protected]>
> >
> > clang static analysis flags a garbage return
> >
> > fs/btrfs/reflink.c:611:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
> > return ret;
> > ^~~~~~~~~~
> > ret will not be set when olen is 0
> > When olen is 0, this function does no work.
> >
> > So initialize ret to 0
> >
> > Signed-off-by: Tom Rix <[email protected]>
>
> Patch itself is good however, the bug cannot currently be triggered, due
> to the following code in the sole caller (btrfs_remap_file_range):
>
>
>
> 15 if (ret < 0 || len == 0)
> 14 goto out_unlock;
> 13
> 12 if (remap_flags & REMAP_FILE_DEDUP)
> 11 ret = btrfs_extent_same(src_inode, off, len, dst_inode, destoff);
> 10 else
> 9 ret = btrfs_clone_files(dst_file, src_file, off,
> len, destoff);
>
> i.e len is guaranteed to be non-zero
Yeah, for that reason I don't think we need to set the value inside
btrfs_extent_same because the caller(s) do the sanity checks.
There are VFS-level checks of the length wrt zero, eg. it won't even
call to copy_file_range from vfs_copy_file_range. The user supplied
length = 0 is interpreted as 'until the end of file' and is properly
reclaculated in generic_remap_file_range_prep.
This looks like clang checker is not able to follow the values accross
function calls, even if the functions are static.