tracing: Use pr_err() instead of WARN() for memory failures

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>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5c701765da5b4d91e83c18dff28ff4fd58b66620..fdb1a9532420dd511643e8f90241089bbbe00442 100644 (file)
--- 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 0a5569b1cace0d33c8ea4e2364fb1d5e88670a99..6a28b1b9bf42c45888869200323c2f47c2116ab6 100644 (file)
--- 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 4812a36affac13dbe3631956f3896f9730614dd1..6bb64d89c32149009a6b9777b9a6ba6e719b105d 100644 (file)
--- 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