On 2023/7/25 04:57, Theodore Ts'o wrote:
On Mon, Jul 24, 2023 at 10:19:02AM -0700, Nick Desaulniers wrote:
err is uninitialized and will be judged when it enters the
loop first time and the condition "!ext4_sb_block_valid()"
is true. Although this can't make problems now, it's better
to correct it.
Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
Hi Su,
Thanks for the patch! I see what the warning is getting at;
If `len <= 0` then `err` is never initialized, then is used at line
4178 (that is UB).
Would you mind sending a v2 with the commit message updated to reflect
the above points? I'd be happy to sign-off on that.
Fortunately, as near as I can tell, ext4_mb_mark_bb() should never be
called with len <= 0. It might be possible to trick ext4 via a
corrupted file system --- I'd have to take a closer look at that, but
fortunately, in the case where len <= 0, bitmap_bh will be NULL, so
regardless of whether err is 0, or some garbage non-zero value,
brelse(NULL) is a no-op.
So while it's good to avoid the clang warning, but the fact that it
might be possible for err to be a "garbage value" shouldn't be causing
any problem.
Maybe it can make the code more robust and clearer. I will send v2 patch
soon.
Thanks for your reply!
Su Hui
Cheers,
- Ted
