lkml.org 
[lkml]   [2022]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC PATCH] rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered
Date
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@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;

/*
--
2.30.2
\
 
 \ /
  Last update: 2022-09-29 16:12    [W:0.064 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site