Merge branch 'bpf: use 32bit safe version of u64_stats'

Eric Dumazet says: ==================== From: Eric Dumazet <[email protected]> Two first patches fix bugs added in 5.1 and 5.5 Third patch replaces the u64 fields in struct bpf_prog_stats with u64_stats_t ones to avoid possible sampling errors, in case of load/store stearing. ==================== Signed-off-by: Alexei Starovoitov <[email protected]>
vieko · Oct 27, 2021 · f9d532f · f9d532f
2 parents 689624f + 61a0aba
commit f9d532f
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Showing 3 changed files with 27 additions and 18 deletions.
diff --git a/include/linux/filter.h b/include/linux/filter.h
@@ -553,9 +553,9 @@ struct bpf_binary_header {
 };
 
 struct bpf_prog_stats {
-	u64 cnt;
-	u64 nsecs;
-	u64 misses;
+	u64_stats_t cnt;
+	u64_stats_t nsecs;
+	u64_stats_t misses;
 	struct u64_stats_sync syncp;
 } __aligned(2 * sizeof(u64));
 
@@ -612,13 +612,14 @@ static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog,
 	if (static_branch_unlikely(&bpf_stats_enabled_key)) {
 		struct bpf_prog_stats *stats;
 		u64 start = sched_clock();
+		unsigned long flags;
 
 		ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
 		stats = this_cpu_ptr(prog->stats);
-		u64_stats_update_begin(&stats->syncp);
-		stats->cnt++;
-		stats->nsecs += sched_clock() - start;
-		u64_stats_update_end(&stats->syncp);
+		flags = u64_stats_update_begin_irqsave(&stats->syncp);
+		u64_stats_inc(&stats->cnt);
+		u64_stats_add(&stats->nsecs, sched_clock() - start);
+		u64_stats_update_end_irqrestore(&stats->syncp, flags);
 	} else {
 		ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
 	}

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
@@ -1804,8 +1804,14 @@ static int bpf_prog_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+struct bpf_prog_kstats {
+	u64 nsecs;
+	u64 cnt;
+	u64 misses;
+};
+
 static void bpf_prog_get_stats(const struct bpf_prog *prog,
-			       struct bpf_prog_stats *stats)
+			       struct bpf_prog_kstats *stats)
 {
 	u64 nsecs = 0, cnt = 0, misses = 0;
 	int cpu;
@@ -1818,9 +1824,9 @@ static void bpf_prog_get_stats(const struct bpf_prog *prog,
 		st = per_cpu_ptr(prog->stats, cpu);
 		do {
 			start = u64_stats_fetch_begin_irq(&st->syncp);
-			tnsecs = st->nsecs;
-			tcnt = st->cnt;
-			tmisses = st->misses;
+			tnsecs = u64_stats_read(&st->nsecs);
+			tcnt = u64_stats_read(&st->cnt);
+			tmisses = u64_stats_read(&st->misses);
 		} while (u64_stats_fetch_retry_irq(&st->syncp, start));
 		nsecs += tnsecs;
 		cnt += tcnt;
@@ -1836,7 +1842,7 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
 {
 	const struct bpf_prog *prog = filp->private_data;
 	char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
-	struct bpf_prog_stats stats;
+	struct bpf_prog_kstats stats;
 
 	bpf_prog_get_stats(prog, &stats);
 	bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
@@ -3577,7 +3583,7 @@ static int bpf_prog_get_info_by_fd(struct file *file,
 	struct bpf_prog_info __user *uinfo = u64_to_user_ptr(attr->info.info);
 	struct bpf_prog_info info;
 	u32 info_len = attr->info.info_len;
-	struct bpf_prog_stats stats;
+	struct bpf_prog_kstats stats;
 	char __user *uinsns;
 	u32 ulen;
 	int err;

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
@@ -545,7 +545,7 @@ static void notrace inc_misses_counter(struct bpf_prog *prog)
 
 	stats = this_cpu_ptr(prog->stats);
 	u64_stats_update_begin(&stats->syncp);
-	stats->misses++;
+	u64_stats_inc(&stats->misses);
 	u64_stats_update_end(&stats->syncp);
 }
 
@@ -586,11 +586,13 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
 	     * Hence check that 'start' is valid.
 	     */
 	    start > NO_START_TIME) {
+		unsigned long flags;
+
 		stats = this_cpu_ptr(prog->stats);
-		u64_stats_update_begin(&stats->syncp);
-		stats->cnt++;
-		stats->nsecs += sched_clock() - start;
-		u64_stats_update_end(&stats->syncp);
+		flags = u64_stats_update_begin_irqsave(&stats->syncp);
+		u64_stats_inc(&stats->cnt);
+		u64_stats_add(&stats->nsecs, sched_clock() - start);
+		u64_stats_update_end_irqrestore(&stats->syncp, flags);
 	}
 }