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 <irogers@google.com>
Link: https://lore.kernel.org/r/20230526183401.2326121-7-irogers@google.com
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ross Zwisler <zwisler@chromium.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 82f53d8..22d34a0 100644 (file)
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -88,7 +88,7 @@ static const char * const bpf_fs__known_mountpoints[] = {
 struct fs {
        const char              *name;
        const char * const      *mounts;
-       char                     path[PATH_MAX];
+       char                    *path;
        bool                     found;
        bool                     checked;
        long                     magic;
@@ -151,17 +151,23 @@ static bool fs__read_mounts(struct fs *fs)
        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);
@@ -188,8 +194,11 @@ static bool fs__check_mounts(struct fs *fs)
        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++;
@@ -227,10 +236,12 @@ static bool fs__env_override(struct fs *fs)
        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;
 }