From: Adam Zabrocki <pi3@pi3.com.pl>
To: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
"David S. Miller" <davem@davemloft.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-kernel@vger.kernel.org, Solar Designer <solar@openwall.com>
Subject: KRETPROBES are broken since the commit 73f9b911faa7
Date: Fri, 15 Apr 2022 20:07:23 +0200 [thread overview]
Message-ID: <20220415180723.GA13921@pi3.com.pl> (raw)
Hello,
The recent KRETPROBE kernel changes introduced a potential NULL pointer
dereference bug when return handler is not set. The root of the problem
are the following commits related to "kprobes: Use rethook for kretprobe
if possible":
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f3a112c0c40dd96d53c8bdf3ea8d94d528f3b7b8
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=73f9b911faa74ac5107879de05c9489c419f41bb
When user sets up a KRETPROBE, kernel eventually ends up here:
static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
struct pt_regs *regs)
{
struct kretprobe *rp = (struct kretprobe *)data;
struct kretprobe_instance *ri;
struct kprobe_ctlblk *kcb;
/* The data must NOT be null. This means rethook data structure is broken. */
if (WARN_ON_ONCE(!data))
return;
__this_cpu_write(current_kprobe, &rp->kp);
kcb = get_kprobe_ctlblk();
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
ri = container_of(rh, struct kretprobe_instance, node);
rp->handler(ri, regs);
__this_cpu_write(current_kprobe, NULL);
}
NOKPROBE_SYMBOL(kretprobe_rethook_handler);
Unfortunately, rp->handler is not verified against NULL. If user does not
set up a return handler, KRETPROBE shouldn't call it (that's the defined
behavior in the documentation, quoting "Any or all handlers can be NULL").
However, kretprobe_rethook_handler function does not enforce such behavior.
I'm going to send a patch for it in a reply to this message.
Thanks,
Adam
--
pi3 (pi3ki31ny) - pi3 (at) itsec pl
http://pi3.com.pl
next reply other threads:[~2022-04-15 18:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-15 18:07 Adam Zabrocki [this message]
2022-04-15 18:10 ` [PATCH] x86/kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set Adam Zabrocki
2022-04-16 14:06 ` Masami Hiramatsu
2022-04-22 13:05 ` Masami Hiramatsu
2022-04-22 13:43 ` Steven Rostedt
2022-04-22 14:54 ` Masami Hiramatsu
2022-04-22 16:35 ` Adam Zabrocki
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