1816936 - Dll Interceptor should write nop instructions to the remaining bytes of the final instruction

Status: RESOLVED FIXED

(Core :: mozglue, defect)

Description

[Greg Stoll :gstoll]

The WindowsDllDetourPatcher overwrites the first 13 (or 10) bytes of a function with a jump to a patched function. If the 13 bytes ends in the middle of an instruction, it leaves the rest of the bytes of that instruction alone, which can cause problems if something else wants to detour that function later. We should instead overwrite the rest of the bytes in that instruction with nop. (or int 3, I suppose)

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:glandium, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 2

[Greg Stoll :gstoll]

In bug 1833793 we discovered that ESET is indeed hooking some of the functions that we do after us. I don't think that this is causing them problems right now, but to be on the safe side I'd like to fix this.

Comment 3

[Greg Stoll :gstoll]

Attachment: Bug 1816936 - make DllInterceptor pad out partial instructions with nop's r=mhowell

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/19e1b7f45acb
make DllInterceptor pad out partial instructions with nop's r=mhowell

Comment 5

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/19e1b7f45acb

Comment 6

[Ryan VanderMeulen [:RyanVM]]

Is this something we should consider backporting anywhere?

Comment 7

[Greg Stoll :gstoll]

Probably not. We don't know of any problems it's causing - well-behaved things that are detouring the functions that we detour should handle this case correctly. And it is a little risky.