From 20a17dd8a0c7ea5b1875d49976cb2a7aac13864a Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Sun, 7 Jun 2026 21:03:55 -0300 Subject: [PATCH] tools lib api: Fix missing null termination in filename__read_int/ull() [ Upstream commit 52b1f9678499b13b7aeb0186d9c6f486c043283f ] filename__read_int() passes a stack buffer to read() using the full sizeof(line) and then hands it to atoi() without null-terminating. If a sysfs file fills the 64-byte buffer exactly, atoi() reads past the array into uninitialized stack memory. filename__read_ull_base() has the same issue with strtoull(). Fix both by reading sizeof(line) - 1 bytes and explicitly null-terminating after a successful read. Fixes: 3a351127cbc682c3 ("tools lib fs: Adopt filename__read_int from tools/perf/") Reported-by: sashiko-bot Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/lib/api/fs/fs.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c index 5cb0eeec2c8a..1ea76e5ba9d4 100644 --- a/tools/lib/api/fs/fs.c +++ b/tools/lib/api/fs/fs.c @@ -293,11 +293,14 @@ int filename__read_int(const char *filename, int *value) { char line[64]; int fd = open(filename, O_RDONLY), err = -1; + ssize_t n; if (fd < 0) return -1; - if (read(fd, line, sizeof(line)) > 0) { + n = read(fd, line, sizeof(line) - 1); + if (n > 0) { + line[n] = '\0'; *value = atoi(line); err = 0; } @@ -311,11 +314,14 @@ static int filename__read_ull_base(const char *filename, { char line[64]; int fd = open(filename, O_RDONLY), err = -1; + ssize_t n; if (fd < 0) return -1; - if (read(fd, line, sizeof(line)) > 0) { + n = read(fd, line, sizeof(line) - 1); + if (n > 0) { + line[n] = '\0'; *value = strtoull(line, NULL, base); if (*value != ULLONG_MAX) err = 0;