From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
commit 448dca8c88755b768552e19bd1618be34ef6d1ff upstream.
These commits use WARN_ON_ONCE() and kill the offending processes when
deprecated and unknown flags are encountered:
commit c17a6ff93213 ("rseq: Kill process when unknown flags are encountered in ABI structures")
commit 0190e4198e47 ("rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags")
The WARN_ON_ONCE() triggered by userspace input prevents use of
Syzkaller to fuzz the rseq system call.
Replace this WARN_ON_ONCE() by pr_warn_once() messages which contain
actually useful information.
Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20221102130635.7379-1-mathieu.desnoyers@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/rseq.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -171,12 +171,27 @@ static int rseq_get_rseq_cs(struct task_
return 0;
}
+static bool rseq_warn_flags(const char *str, u32 flags)
+{
+ u32 test_flags;
+
+ if (!flags)
+ return false;
+ test_flags = flags & RSEQ_CS_NO_RESTART_FLAGS;
+ if (test_flags)
+ pr_warn_once("Deprecated flags (%u) in %s ABI structure", test_flags, str);
+ test_flags = flags & ~RSEQ_CS_NO_RESTART_FLAGS;
+ if (test_flags)
+ pr_warn_once("Unknown flags (%u) in %s ABI structure", test_flags, str);
+ return true;
+}
+
static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
{
u32 flags, event_mask;
int ret;
- if (WARN_ON_ONCE(cs_flags & RSEQ_CS_NO_RESTART_FLAGS) || cs_flags)
+ if (rseq_warn_flags("rseq_cs", cs_flags))
return -EINVAL;
/* Get thread flags. */
@@ -184,7 +199,7 @@ static int rseq_need_restart(struct task
if (ret)
return ret;
- if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS) || flags)
+ if (rseq_warn_flags("rseq", flags))
return -EINVAL;
/*
