Messages in this thread | | | Date | Tue, 6 Jul 2004 08:04:36 -0300 | From | Marcelo Tosatti <> | Subject | Re: question about /proc/<PID>/mem in 2.4 |
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On Tue, Jul 06, 2004 at 12:14:04PM +0100, Tigran Aivazian wrote: > On Mon, 5 Jul 2004, FabF wrote: > > > Surely, the super user (i.e. CAP_SYS_PTRACE in this context) should be > > > allowed to read any process' memory without having to do the > > > PTRACE_ATTACH/PTRACE_PEEKUSER kind of thing which strace(8) is doing? > > > > FYI may_ptrace_attach plugged somewhere between 2.4.21 & 22.This one get > > used as is (ie without MAY_PTRACE) in proc_pid_environ but dunno about > > reason why CAP_SYS_PTRACE isn't authoritative elsewhere. > > Ok, but still nobody seems to know why the super user is not allowed to > access /proc/<PID>/mem of any task. Any code which nobody in the world > knows the reason for, is broken and should be removed. > > I will wait a few weeks to see if someone does come up with the reason for > that "extra secure" check in mem_read() and if nobody has objections I'll > send Linus a patch to relax the check to a more reasonable one, namely to > allow CAP_SYS_PTRACE process to bypass any other conditions imposed.
Hi Tigran,
This code was added to stop the ptrace/kmod vulnerabilities. I do not fully understand the issues around tsk->is_dumpable and the fix itself, but I agree on that the checks here could be relaxed for the super user.
However changing it to
if (!is_dumpable(task) && !capable(CAP_SYS_PTRACE)) goto out;
Seems wrong because this will stop always honoring the tsk->is_dumpable flag. (?)
Alan for sure can make the picture clear - he wrote this thing.
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