Merge pull request #20763 from poettering/fileio-test

test-fileio: test read_virtual_file() with more files from /proc

2 files changed, 18 insertions, 5 deletions

diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index e69b888315..60a9885108 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -470,9 +470,14 @@ int read_virtual_file(const char *filename, size_t max_size, char **ret_contents
                 if (n <= size)
                         break;
 
-                /* If a maximum size is specified and we already read as much, no need to try again */
-                if (max_size != SIZE_MAX && n >= max_size) {
-                        n = max_size;
+                /* If a maximum size is specified and we already read more we know the file is larger, and
+                 * can handle this as truncation case. Note that if the size of what we read equals the
+                 * maximum size then this doesn't mean truncation, the file might or might not end on that
+                 * byte. We need to rerun the loop in that case, with a larger buffer size, so that we read
+                 * at least one more byte to be able to distinguish EOF from truncation. */
+                if (max_size != SIZE_MAX && n > max_size) {
+                        n = size; /* Make sure we never use more than what we sized the buffer for (so that
+                                   * we have one free byte in it for the trailing NUL we add below).*/
                         truncated = true;
                         break;
                 }
diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c
index 2b6ef495aa..fa8a66df04 100644
--- a/src/test/test-fileio.c
+++ b/src/test/test-fileio.c
@@ -1047,7 +1047,11 @@ static void test_read_virtual_file(size_t max_size) {
         FOREACH_STRING(filename,
                        "/proc/1/cmdline",
                        "/etc/nsswitch.conf",
-                       "/sys/kernel/uevent_seqnum") {
+                       "/sys/kernel/uevent_seqnum",
+                       "/proc/kcore",
+                       "/proc/kallsyms",
+                       "/proc/self/exe",
+                       "/proc/self/pagemap") {
 
                 _cleanup_free_ char *buf = NULL;
                 size_t size = 0;
@@ -1055,7 +1059,11 @@ static void test_read_virtual_file(size_t max_size) {
                 r = read_virtual_file(filename, max_size, &buf, &size);
                 if (r < 0) {
                         log_info_errno(r, "read_virtual_file(\"%s\", %zu): %m", filename, max_size);
-                        assert_se(ERRNO_IS_PRIVILEGE(r) || r == -ENOENT);
+                        assert_se(ERRNO_IS_PRIVILEGE(r) || /* /proc/kcore is not accessible to unpriv */
+                                  IN_SET(r,
+                                         -ENOENT,  /* Some of the files might be absent */
+                                         -EINVAL,  /* too small reads from /proc/self/pagemap trigger EINVAL */
+                                         -EFBIG)); /* /proc/kcore and /proc/self/pagemap should be too large */
                 } else
                         log_info("read_virtual_file(\"%s\", %zu): %s (%zu bytes)", filename, max_size, r ? "non-truncated" : "truncated", size);
         }