Check fgets(3) return value

When fgets() function fails, contents of the buffer is undefined.  That
is, fgets() return value needs to be checked, to avoid undefined behavior.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index 190c4b7..d701615 100644 (file)
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -789,7 +789,8 @@ static void modify_u8(char *com, const char *prompt,
 
        sprintf(buf, format, *val);
        printf("%30s    [%s] ", prompt, buf);
-       fgets(buf, sizeof(buf), stdin);
+       if (!fgets(buf, sizeof(buf), stdin))
+               return;
        if (buf[strlen (buf) - 1] == '\n')
                buf[strlen (buf) - 1] = '\0';
        if (!buf[0])
@@ -810,7 +811,8 @@ static void modify_u16(char *com, const char *prompt,
 
        sprintf(buf, format, *val);
        printf("%30s    [%s] ", prompt, buf);
-       fgets(buf, sizeof(buf), stdin);
+       if (!fgets(buf, sizeof(buf), stdin))
+               return;
        if (buf[strlen (buf) - 1] == '\n')
                buf[strlen (buf) - 1] = '\0';
        if (!buf[0])
@@ -831,7 +833,8 @@ static void modify_u32(char *com, const char *prompt,
 
        sprintf(buf, format, *val);
        printf("%30s    [%s] ", prompt, buf);
-       fgets(buf, sizeof(buf), stdin);
+       if (!fgets(buf, sizeof(buf), stdin))
+               return;
        if (buf[strlen (buf) - 1] == '\n')
                buf[strlen (buf) - 1] = '\0';
        if (!buf[0])

diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index 24246e0..cb563fd 100644 (file)
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -251,10 +251,8 @@ static int is_swap_device(const char *file)
        if (!(f = fopen("/proc/swaps", "r")))
                return 0;
        /* Skip the first line */
-       fgets(buf, sizeof(buf), f);
-       while (!feof(f)) {
-               if (!fgets(buf, sizeof(buf), f))
-                       break;
+       if (fgets(buf, sizeof(buf), f))
+       while (fgets(buf, sizeof(buf), f)) {
                if ((cp = strchr(buf, ' ')) != NULL)
                        *cp = 0;
                if ((cp = strchr(buf, '\t')) != NULL)

diff --git a/misc/util.c b/misc/util.c
index 6a4c40c..7c99a2a 100644 (file)
--- a/misc/util.c
+++ b/misc/util.c
@@ -71,8 +71,8 @@ void proceed_question(void)
        fflush(stderr);
        fputs(_("Proceed anyway? (y,n) "), stdout);
        buf[0] = 0;
-       fgets(buf, sizeof(buf), stdin);
-       if (strchr(short_yes, buf[0]) == 0)
+       if (!fgets(buf, sizeof(buf), stdin) ||
+           strchr(short_yes, buf[0]) == 0)
                exit(1);
 }