Messages in this thread Patch in this message | | | Date | Sat, 22 Mar 2003 14:10:06 +0000 | From | Russell King <> | Subject | Re: 2.4+ptrace exploit fix breaks root's ability to strace |
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On Sat, Mar 22, 2003 at 02:58:51PM +0000, Alan Cox wrote: > On Sat, 2003-03-22 at 10:31, Russell King wrote: > > Are the authors of the ptrace patch aware that, in addition to closing the > > hole, the "fix" also prevents a ptrace-capable task (eg, strace started by > > root) from ptracing user threads? > > > > For example, you can't strace vsftpd processes started from xinetd. > > > > Is this intended behaviour? > > Its an unintended side effect, nobody has sent a patch to fix it yet.
How about this fix? PT_PTRACE_CAP is set when we attach to a process and the process doing the attaching has the ptrace capability.
Note that this patch is against the 2.4.19 version of ptrace.c with the 2.4.20 ptrace patch applied.
--- orig/kernel/ptrace.c Wed Mar 19 15:54:45 2003 +++ linux/kernel/ptrace.c Sat Mar 22 10:14:01 2003 @@ -22,7 +22,7 @@ int ptrace_check_attach(struct task_struct *child, int kill) { mb(); - if (!is_dumpable(child)) + if (!is_dumpable(child) && !(child->ptrace & PT_PTRACE_CAP)) return -EPERM; if (!(child->ptrace & PT_PTRACED)) @@ -140,7 +140,7 @@ /* Worry about races with exit() */ task_lock(tsk); mm = tsk->mm; - if (!is_dumpable(tsk) || (&init_mm == mm)) + if ((!is_dumpable(tsk) || (&init_mm == mm)) && !(tsk->ptrace & PT_PTRACE_CAP)) mm = NULL; if (mm) atomic_inc(&mm->mm_users);
-- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
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