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kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set 

The recent kernel change in 73f9b911fa ("kprobes: Use rethook for kretprobe
if possible"), introduced a potential NULL pointer dereference bug in the
KRETPROBE mechanism. The official Kprobes documentation defines that "Any or
all handlers can be NULL". Unfortunately, there is a missing return handler
verification to fulfill these requirements and can result in a NULL pointer
dereference bug.

This patch adds such verification in kretprobe_rethook_handler() function.

Fixes: 73f9b911fa ("kprobes: Use rethook for kretprobe if possible")
Signed-off-by: Adam Zabrocki <pi3@pi3.com.pl>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Anil S. Keshavamurthy <anil.s.keshavamurthy@intel.com>
Link: https://lore.kernel.org/bpf/20220422164027.GA7862@pi3.com.pl
This commit is contained in:
Adam Zabrocki 2022-04-22 18:40:27 +02:00 committed by Daniel Borkmann
parent b02d196c44
commit 1d661ed54d
1 changed files with 1 additions and 1 deletions
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2
kernel/kprobes.c
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@ -2126,7 +2126,7 @@ static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
struct kprobe_ctlblk *kcb;
/* The data must NOT be null. This means rethook data structure is broken. */
if (WARN_ON_ONCE(!data))
if (WARN_ON_ONCE(!data) || !rp->handler)
return;
__this_cpu_write(current_kprobe, &rp->kp);