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perf machine: Check snprintf truncation for guest kallsyms path

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machines__create_guest_kernel_maps() builds the guest kallsyms path
with snprintf() without checking the return value.  A truncated path
could pass the access() check if a prefix directory happens to contain
a file named "kallsyms", leading to the wrong file being used for
symbol resolution.

Check for truncation and skip the directory.

Fixes: a1645ce12a ("perf: 'perf kvm' tool for monitoring guest performance from host")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Zhang, Yanmin <yanmin_zhang@linux.intel.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Arnaldo Carvalho de Melo 2026-07-26 20:40:14 -03:00 committed by Namhyung Kim
parent f53bf58dcd
commit d04ef71492
1 changed files with 8 additions and 3 deletions
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11
tools/perf/util/machine.c
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@ -1269,9 +1269,14 @@ int machines__create_guest_kernel_maps(struct machines *machines)
free(namelist[i]);
continue;
}
snprintf(path, sizeof(path), "%s/%s/proc/kallsyms",
symbol_conf.guestmount,
namelist[i]->d_name);
if (snprintf(path, sizeof(path), "%s/%s/proc/kallsyms",
symbol_conf.guestmount,
namelist[i]->d_name) >= (int)sizeof(path)) {
pr_debug("Guest kallsyms path too long for %s. Skipping.\n",
namelist[i]->d_name);
free(namelist[i]);
continue;
}
if (access(path, R_OK)) {
pr_debug("Can't access file %s\n", path);
free(namelist[i]);