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Subject[for-next][PATCH 7/7] tracing: Use pr_err() instead of WARN() for memory failures
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

As warnings can trigger panics, especially when "panic_on_warn" is set,
memory failure warnings can cause panics and fail fuzz testers that are
stressing memory.

Create a MEM_FAIL() macro to use instead of WARN() in the tracing code
(perhaps this should be a kernel wide macro?), and use that for memory
failure issues. This should stop failing fuzz tests due to warnings.

Link: https://lore.kernel.org/r/CACT4Y+ZP-7np20GVRu3p+eZys9GPtbu+JpfV+HtsufAzvTgJrg@mail.gmail.com

Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 4 ++--
kernel/trace/trace.c | 18 +++++++++---------
kernel/trace/trace.h | 12 ++++++++++++
3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5c701765da5b..fdb1a9532420 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5459,7 +5459,7 @@ static void __init set_ftrace_early_graph(char *buf, int enable)
struct ftrace_hash *hash;

hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
- if (WARN_ON(!hash))
+ if (MEM_FAIL(!hash, "Failed to allocate hash\n"))
return;

while (buf) {
@@ -6591,7 +6591,7 @@ static void add_to_clear_hash_list(struct list_head *clear_list,

func = kmalloc(sizeof(*func), GFP_KERNEL);
if (!func) {
- WARN_ONCE(1, "alloc failure, ftrace filter could be stale\n");
+ MEM_FAIL(1, "alloc failure, ftrace filter could be stale\n");
return;
}

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0a5569b1cace..6a28b1b9bf42 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3126,7 +3126,7 @@ static int alloc_percpu_trace_buffer(void)
struct trace_buffer_struct *buffers;

buffers = alloc_percpu(struct trace_buffer_struct);
- if (WARN(!buffers, "Could not allocate percpu trace_printk buffer"))
+ if (MEM_FAIL(!buffers, "Could not allocate percpu trace_printk buffer"))
return -ENOMEM;

trace_percpu_buffer = buffers;
@@ -7932,7 +7932,7 @@ static struct dentry *tracing_dentry_percpu(struct trace_array *tr, int cpu)

tr->percpu_dir = tracefs_create_dir("per_cpu", d_tracer);

- WARN_ONCE(!tr->percpu_dir,
+ MEM_FAIL(!tr->percpu_dir,
"Could not create tracefs directory 'per_cpu/%d'\n", cpu);

return tr->percpu_dir;
@@ -8253,7 +8253,7 @@ create_trace_option_files(struct trace_array *tr, struct tracer *tracer)
for (cnt = 0; opts[cnt].name; cnt++) {
create_trace_option_file(tr, &topts[cnt], flags,
&opts[cnt]);
- WARN_ONCE(topts[cnt].entry == NULL,
+ MEM_FAIL(topts[cnt].entry == NULL,
"Failed to create trace option: %s",
opts[cnt].name);
}
@@ -8437,7 +8437,7 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
#ifdef CONFIG_TRACER_MAX_TRACE
ret = allocate_trace_buffer(tr, &tr->max_buffer,
allocate_snapshot ? size : 1);
- if (WARN_ON(ret)) {
+ if (MEM_FAIL(ret, "Failed to allocate trace buffer\n")) {
ring_buffer_free(tr->array_buffer.buffer);
tr->array_buffer.buffer = NULL;
free_percpu(tr->array_buffer.data);
@@ -8726,7 +8726,7 @@ static __init void create_trace_instances(struct dentry *d_tracer)
trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
instance_mkdir,
instance_rmdir);
- if (WARN_ON(!trace_instance_dir))
+ if (MEM_FAIL(!trace_instance_dir, "Failed to create instances directory\n"))
return;
}

@@ -8796,7 +8796,7 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
#endif

if (ftrace_create_function_files(tr, d_tracer))
- WARN(1, "Could not allocate function filter files");
+ MEM_FAIL(1, "Could not allocate function filter files");

#ifdef CONFIG_TRACER_SNAPSHOT
trace_create_file("snapshot", 0644, d_tracer,
@@ -9348,8 +9348,7 @@ __init static int tracer_alloc_buffers(void)

/* TODO: make the number of buffers hot pluggable with CPUS */
if (allocate_trace_buffers(&global_trace, ring_buf_size) < 0) {
- printk(KERN_ERR "tracer: failed to allocate ring buffer!\n");
- WARN_ON(1);
+ MEM_FAIL(1, "tracer: failed to allocate ring buffer!\n");
goto out_free_savedcmd;
}

@@ -9422,7 +9421,8 @@ void __init early_trace_init(void)
if (tracepoint_printk) {
tracepoint_print_iter =
kmalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL);
- if (WARN_ON(!tracepoint_print_iter))
+ if (MEM_FAIL(!tracepoint_print_iter,
+ "Failed to allocate trace iterator\n"))
tracepoint_printk = 0;
else
static_key_enable(&tracepoint_printk_key.key);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 4812a36affac..6bb64d89c321 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -94,6 +94,18 @@ enum trace_type {

#include "trace_entries.h"

+/* Use this for memory failure errors */
+#define MEM_FAIL(condition, fmt, ...) ({ \
+ static bool __section(.data.once) __warned; \
+ int __ret_warn_once = !!(condition); \
+ \
+ if (unlikely(__ret_warn_once && !__warned)) { \
+ __warned = true; \
+ pr_err("ERROR: " fmt, ##__VA_ARGS__); \
+ } \
+ unlikely(__ret_warn_once); \
+})
+
/*
* syscalls are special, and need special handling, this is why
* they are not included in trace_entries.h
--
2.24.1

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