David Miller wrote:
From: Chuck Lever <[EMAIL PROTECTED]>
Date: Mon, 05 Nov 2007 18:59:26 -0500
If that's truly the case, document the requirement (perhaps using
something the compiler itself can verify) instead of using a clever
type cast trick.
Feel free to submit such a change.
Here's what I propose.
skb->truesize should be an int, not an unsigned int, since you expect
that it may go below zero.
Explicitly assert that skb->truesize is greater than zero in
skb_truesize_check().
Explicitly assert that skb->len + sizeof(sk_buff) is less than INT_MAX.
Leave the assertion that's already there, but ensure that the types on
both side of the comparison are as we expect.
Thoughts?
Here's the problem with leaving these little surprises in commonly used
kernel headers. Suppose the developer of a network driver or network
file system that uses one of these headers wants to employ static code
analysis to identify issues introduced by new patches to their
subsystem. The tool warnings generated in kernel headers are just
noise, and make using such code analysis difficult.
Here's the problem with submitting patches fixing non-bugs and
removing useful assertions from kernel. I won't apply them.
"removing useful assertions"
The (int) type cast in that assertion is nothing more than a comment.
The compiler promotes that side of the comparison to match the type on
the right side, and the explicit type cast is entirely ignored. So in
fact, my patch removed nothing but a mistaken assumption. The assertion
behaves the same after my patch as it did before.
Thus anyone might be confused at what exactly was being asserted in
skb_truesize_check(). It's not a question of whether or not I reviewed
the logic that uses skb->truesize before crafting my patch; I did review
it. The fact that skb_truesize_check() never before asserted that
skb->truesize is greater than zero is not my fault.
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