selftests/x86/lam: Zero out buffer for readlink()

[ Upstream commit 29060633411a02f6f2dd9d5245919385d69d81f0 ]

Zero out the buffer for readlink() since readlink() does not append a
terminating null byte to the buffer.  Also change the buffer length
passed to readlink() to 'PATH_MAX - 1' to ensure the resulting string
is always null terminated.

Fixes: 833c12ce0f430 ("selftests/x86/lam: Add inherit test cases for linear-address masking")
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20231016062446.695-1-binbin.wu@linux.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
index eb0e469..8f9b06d 100644 (file)
--- a/tools/testing/selftests/x86/lam.c
+++ b/tools/testing/selftests/x86/lam.c
@@ -573,7 +573,7 @@ int do_uring(unsigned long lam)
        char path[PATH_MAX] = {0};
 
        /* get current process path */
-       if (readlink("/proc/self/exe", path, PATH_MAX) <= 0)
+       if (readlink("/proc/self/exe", path, PATH_MAX - 1) <= 0)
                return 1;
 
        int file_fd = open(path, O_RDONLY);
@@ -680,14 +680,14 @@ static int handle_execve(struct testcases *test)
                perror("Fork failed.");
                ret = 1;
        } else if (pid == 0) {
-               char path[PATH_MAX];
+               char path[PATH_MAX] = {0};
 
                /* Set LAM mode in parent process */
                if (set_lam(lam) != 0)
                        return 1;
 
                /* Get current binary's path and the binary was run by execve */
-               if (readlink("/proc/self/exe", path, PATH_MAX) <= 0)
+               if (readlink("/proc/self/exe", path, PATH_MAX - 1) <= 0)
                        exit(-1);
 
                /* run binary to get LAM mode and return to parent process */