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SubjectRe: [PATCH] proc: allow killing processes via file descriptors

> On Nov 18, 2018, at 12:44 PM, Daniel Colascione <> wrote:

> That is, I'm proposing an API that looks like this:
> int process_kill(int procfs_dfd, int signo, const union sigval value)
> If, later, process_kill were to *also* accept process-capability FDs,
> nothing would break.

Except that this makes it ambiguous to the caller as to whether their current creds are considered. So it would need to be a different syscall or at least a flag. Otherwise a lot of those nice theoretical properties go away.

> Yes, that's what I have in mind. A siginfo_t is small enough that we
> could just store it as a blob allocated off the procfs inode or
> something like that without bothering with a shmfs file. You'd be able
> to read(2) the exit status as many times as you wanted.

I think that, if the syscall in question is read(2), then it should work *once* per struct file. Otherwise running cat on the file would behave very oddly.

Read and poll have the same problem as write: we can’t check caps in read or poll either.
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