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SubjectRe: [PATCH] ocfs2: dereference before NULL check in ocfs2_direct_IO_get_blocks()
Alexey Dobriyan wrote:
> AFAICS, the patch is BS, as usual with this type of patches.
>
You missed the full purpose: the patch makes a function consistent about
its own assumptions (but leaves them in place since they're on the
better-safe-than-sorry side). It addresses assumptions inconsistency
(confusing for both human readers and static analysis tools) just as
much as it addresses a possible bug. Regardless of whether "inode" &
"bh_result" can be NULL, I don't think the following is OK (coding-wise):

unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;

if (!inode || !bh_result) {
mlog(ML_ERROR, "inode or bh_result is null\n");
return -EIO;
}


> Can "inode" and "bh_result" be NULL here? I bet they can't
Great, then the NULL branch is dead code and we can fix consistency
differently:

Signed-off-by: Florin Malita <fmalita@gmail.com>
---

fs/ocfs2/aops.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 47152bf..370c241 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -558,16 +558,9 @@ static int ocfs2_direct_IO_get_blocks(st
u64 vbo_max; /* file offset, max_blocks from iblock */
u64 p_blkno;
int contig_blocks;
- unsigned char blocksize_bits;
+ unsigned char blocksize_bits = inode->i_sb->s_blocksize_bits;
unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;

- if (!inode || !bh_result) {
- mlog(ML_ERROR, "inode or bh_result is null\n");
- return -EIO;
- }
-
- blocksize_bits = inode->i_sb->s_blocksize_bits;
-
/* This function won't even be called if the request isn't all
* nicely aligned and of the right size, so there's no need
* for us to check any of that. */

-
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