From fe63d3bca288c5bb983304efd5fc3a5ff3183403 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Sat, 13 Jun 2026 13:59:39 -0300 Subject: [PATCH] perf machine: Use snprintf() for guestmount path construction machines__findnew() and machines__create_guest_kernel_maps() use sprintf() to build paths by prepending symbol_conf.guestmount. Both write into PATH_MAX stack buffers, but guestmount comes from user configuration and is not length-checked. A guestmount path at or near PATH_MAX causes a stack buffer overflow. Switch to snprintf() with sizeof() to prevent overflow. The subsequent access()/fopen() calls will fail on a truncated path. Fixes: a1645ce12adb6c9c ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/machine.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 9329d319bd033..0d2ebf6a84bcf 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -333,7 +333,7 @@ struct machine *machines__findnew(struct machines *machines, pid_t pid) if ((pid != HOST_KERNEL_ID) && (pid != DEFAULT_GUEST_KERNEL_ID) && (symbol_conf.guestmount)) { - sprintf(path, "%s/%d", symbol_conf.guestmount, pid); + snprintf(path, sizeof(path), "%s/%d", symbol_conf.guestmount, pid); if (access(path, R_OK)) { static struct strlist *seen; @@ -1260,9 +1260,9 @@ int machines__create_guest_kernel_maps(struct machines *machines) namelist[i]->d_name); continue; } - sprintf(path, "%s/%s/proc/kallsyms", - symbol_conf.guestmount, - namelist[i]->d_name); + snprintf(path, sizeof(path), "%s/%s/proc/kallsyms", + symbol_conf.guestmount, + namelist[i]->d_name); ret = access(path, R_OK); if (ret) { pr_debug("Can't access file %s\n", path); -- 2.47.3