linux-kernel - [PATCH v2 06/16] tools api fs: Avoid large static PATH

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Message-Id: <20230526183401.2326121-7-irogers@google.com>
Date:   Fri, 26 May 2023 11:33:51 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Ross Zwisler <zwisler@...omium.org>,
        Leo Yan <leo.yan@...aro.org>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Yang Jihong <yangjihong1@...wei.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [PATCH v2 06/16] 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@...gle.com>
---
 tools/lib/api/fs/fs.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 82f53d81a7a7..22d34a0be8b4 100644
--- 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;
 }
 
-- 
2.41.0.rc0.172.g3f132b7071-goog