Re: [PATCH v2] ext4: fix bug in extents parsing when eh_entries == 0 and eh_depth > 0

From: Baokun Li
Date: Fri Aug 12 2022 - 09:35:00 EST


Hi Luís,


On 8/12/2022 9:19 PM, Luís Henriques wrote:
Hi Baokun!

On Fri, Aug 12, 2022 at 08:50:34PM +0800, Baokun Li wrote:
Hi Luís,
...
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 53cfe2c681c4..a5457ac1999c 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -460,6 +460,11 @@ static int __ext4_ext_check(const char *function, unsigned int line,
error_msg = "invalid eh_entries";
goto corrupted;
}
+ if (unlikely((le16_to_cpu(eh->eh_entries) == 0) &&
+ (le16_to_cpu(eh->eh_depth > 0)))) {

le16_to_cpu(eh->eh_depth > 0) It's the wrong position of the parentheses here.

The parentheses are misplaced,
I'm not sure I understand what you mean. I want to have

if (unlikely((CONDITION A) && (CONDITION B))) {
/* ... */
}

so they look correct. Or is that a matter of style/alignment? (Which
checkpatch.pl doesn't complains about, by the way.)

and le16_to_cpu is not needed here.
OK, I guess that, since both conditions do a comparison against '0', the
le16_to_cpu() can be dropped. And, if the parentheses problem you
mentioned above is a style problem, dropping it will also solve it because
that statement will become

if (unlikely((eh->eh_entries == 0) && (eh->eh_depth > 0))) {
/* ... */
}

Yeah, but it could be more streamlined here.

The earlier judgment has guaranteed "depth == eh->eh_depth"

And once again, thanks for your review!

Cheers,

--
With Best Regards,
Baokun Li