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rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered

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These commits use WARN_ON_ONCE() and kill the offending processes when
deprecated and unknown flags are encountered:

commit c17a6ff932 ("rseq: Kill process when unknown flags are encountered in ABI structures")
commit 0190e4198e ("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@arm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20221102130635.7379-1-mathieu.desnoyers@efficios.com
This commit is contained in:
Mathieu Desnoyers 2022-11-02 09:06:35 -04:00 committed by Peter Zijlstra
parent 094226ad94
commit 448dca8c88
1 changed files with 17 additions and 2 deletions
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19
kernel/rseq.c
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@ -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;
/*