Re: [RFC PATCH] rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered
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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: 2022-10-21 02:11:56
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On 2022-09-29 10:12, Mathieu Desnoyers wrote:
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.Hi Peter, Should I resubmit this or can you simply pick up the Acked-by from Paul McKenney and Mark Rutland and route this through the tip tree ? Thanks, Mathieu
quoted hunk ↗ jump to hunk
Reported-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> --- kernel/rseq.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)diff --git a/kernel/rseq.c b/kernel/rseq.c index bda8175f8f99..d38ab944105d 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c@@ -171,12 +171,27 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) 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_struct *t, u32 cs_flags) if (ret) return ret; - if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS) || flags) + if (rseq_warn_flags("rseq", flags)) return -EINVAL; /*
-- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com