[unix-junkie]

I don't get it, it seems to me that this fix is incorrect.

It's pointless to check for such a signed integer overflow after it happened.

[bcoates]

I think you're right, unless nginx uses --fwrapv or it's equivalent on every compiler.

[lysium]

Why is length stored with a signed integer in the first place?

[tptacek]

It's (mis)using off_t, which allows for negative offsets (for obvious reasons). You also don't need signed integers to have integer overflows.