tools api fs: Avoid large static PATH_MAX arrays

Change struct fs to have a pointer to a dynamically allocated array
rather than an array. This reduces the size of fs__entries from 24,768
bytes to 240 bytes. Read paths into a stack allocated array and
strdup. Fix off-by-1 fscanf %<num>s in fs__read_mounts caught by
address sanitizer.

Signed-off-by: Ian Rogers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Cc: K Prateek Nayak <[e-mail]>
Cc: Ravi Bangoria <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Ross Zwisler <[e-mail]>
Cc: Steven Rostedt (Google) <[e-mail]>
Cc: Sean Christopherson <[e-mail]>
Cc: Yang Jihong <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Masami Hiramatsu (Google) <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Tiezhu Yang <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/api/fs/fs.c

···
 struct fs {
 	const char		*name;
 	const char * const	*mounts;
-	char			 path[PATH_MAX];
+	char			*path;
 	bool			 found;
 	bool			 checked;
 	long			 magic;
···
 	bool found = false;
 	char type[100];
 	FILE *fp;
+	char path[PATH_MAX + 1];
 
 	fp = fopen("/proc/mounts", "r");
 	if (fp == NULL)
-		return NULL;
+		return false;
 
 	while (!found &&
 	       fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
-		      fs->path, type) == 2) {
+		      path, type) == 2) {
 
-		if (strcmp(type, fs->name) == 0)
+		if (strcmp(type, fs->name) == 0) {
+			free(fs->path);
+			fs->path = strdup(path);
+			if (!fs->path)
+				return false;
 			found = true;
+		}
 	}
 
 	fclose(fp);
···
 	ptr = fs->mounts;
 	while (*ptr) {
 		if (fs__valid_mount(*ptr, fs->magic) == 0) {
+			free(fs->path);
+			fs->path = strdup(*ptr);
+			if (!fs->path)
+				return false;
 			fs->found = true;
-			strcpy(fs->path, *ptr);
 			return true;
 		}
 		ptr++;
···
 	if (!override_path)
 		return false;
 
+	free(fs->path);
+	fs->path = strdup(override_path);
+	if (!fs->path)
+		return false;
 	fs->found = true;
 	fs->checked = true;
-	strncpy(fs->path, override_path, sizeof(fs->path) - 1);
-	fs->path[sizeof(fs->path) - 1] = '\0';
 	return true;
 }