[Webkit-unassigned] [Bug 153235] [Linux] Seccomp filters: safely allocate all memory used by web process signal handler

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=153235

Thiago Marcos P. Santos <tmpsantos at gmail.com> changed:

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--- Comment #1 from Thiago Marcos P. Santos <tmpsantos at gmail.com> ---
I think you can, because it a synchronous signal. You have total control of when the thread will jump into the signal handler. Think of it like "open()" calling a wrapper before doing the actual "open()".

The problem would be if you have to handle a SIGSYS (or pretty much any other signal) not emitted by a seccomp fault and you allocate memory.

In this case your program could be preempted on any state, including in the middle of a memory allocation.

This premiss is the reason why the whole thing works in the first place.


The problem I see would be if you call "malloc()" and malloc does some funny stuff and ultimately call a function that triggers a SIGSYS before returning. In this case things will go wrong because malloc data structures could be in a fragile state, but I suppose memory allocators will only do "brk()" and "memmap()" anonymous and you are not catching these.

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