fdisk: fix a case where we can inadvertently close /proc/partitions fd early

2 files changed, 29 insertions, 19 deletions

diff --git a/util-linux/fdisk.c b/util-linux/fdisk.c
index 57d4d653e..50ab48dab 100644
--- a/util-linux/fdisk.c
+++ b/util-linux/fdisk.c
@@ -36,6 +36,18 @@
 #define LINUX_LVM       0x8e
 #define LINUX_RAID      0xfd
 
+
+enum {
+        OPT_b = 1 << 0,
+        OPT_C = 1 << 1,
+        OPT_H = 1 << 2,
+        OPT_l = 1 << 3,
+        OPT_S = 1 << 4,
+        OPT_u = 1 << 5,
+        OPT_s = (1 << 6) * ENABLE_FEATURE_FDISK_BLKSIZE,
+};
+
+
 /* Used for sector numbers. Today's disk sizes make it necessary */
 typedef unsigned long long ullong;
 
@@ -366,6 +378,13 @@ static ullong bb_BLKGETSIZE_sectors(int fd)
                 s |= (sector >> 2) & 0xc0;   \
         } while (0)
 
+static void
+close_dev_fd(void)
+{
+        /* Not really closing, but making sure it is open, and to harmless place */
+        xmove_fd(xopen(bb_dev_null, O_RDONLY), dev_fd);
+}
+
 #if ENABLE_FEATURE_FDISK_WRITABLE
 /* read line; return 0 or first printable char */
 static int
@@ -660,7 +679,7 @@ static ullong total_number_of_sectors;
 static void fdisk_fatal(const char *why)
 {
         if (listing) {
-                close(dev_fd);
+                close_dev_fd();
                 longjmp(listingbuf, 1);
         }
         bb_error_msg_and_die(why, disk_device);
@@ -1280,12 +1299,12 @@ static int get_boot(void)
                                 return 1;
                         fdisk_fatal(unable_to_open);
                 }
-                xmove_fd(fd, dev_fd);
                 printf("'%s' is opened for read only\n", disk_device);
         }
+        xmove_fd(fd, dev_fd);
         if (512 != read(dev_fd, MBRbuffer, 512)) {
                 if (what == TRY_ONLY) {
-                        close(dev_fd);
+                        close_dev_fd();
                         return 1;
                 }
                 fdisk_fatal(unable_to_read);
@@ -2466,7 +2485,7 @@ reread_partition_table(int leave)
 
         if (leave) {
                 if (ENABLE_FEATURE_CLEAN_UP)
-                        close(dev_fd);
+                        close_dev_fd();
                 exit(i != 0);
         }
 }
@@ -2599,7 +2618,7 @@ xselect(void)
                         break;
                 case 'q':
                         if (ENABLE_FEATURE_CLEAN_UP)
-                                close(dev_fd);
+                                close_dev_fd();
                         bb_putchar('\n');
                         exit(0);
                 case 'r':
@@ -2708,7 +2727,7 @@ open_list_and_close(const char *device, int user_specified)
 #endif
         }
  ret:
-        close(dev_fd);
+        close_dev_fd();
 }
 
 /* for fdisk -l: try all things in /proc/partitions
@@ -2758,19 +2777,9 @@ int fdisk_main(int argc, char **argv)
          *
          * Options -C, -H, -S set the geometry.
          */
-        enum {
-                OPT_b = 1 << 0,
-                OPT_C = 1 << 1,
-                OPT_H = 1 << 2,
-                OPT_l = 1 << 3,
-                OPT_S = 1 << 4,
-                OPT_u = 1 << 5,
-                OPT_s = (1 << 6) * ENABLE_FEATURE_FDISK_BLKSIZE,
-        };
-
         INIT_G();
 
-        close(dev_fd); /* just in case */
+        close_dev_fd(); /* needed: fd 3 must not stay closed */
 
         opt_complementary = "b+:C+:H+:S+"; /* numeric params */
         opt = getopt32(argv, "b:C:H:lS:u" USE_FEATURE_FDISK_BLKSIZE("s"),
@@ -2933,7 +2942,8 @@ int fdisk_main(int argc, char **argv)
                         list_table(0);
                         break;
                 case 'q':
-                        close(dev_fd);
+                        if (ENABLE_FEATURE_CLEAN_UP)
+                                close_dev_fd();
                         bb_putchar('\n');
                         return 0;
                 case 's':
diff --git a/util-linux/fdisk_osf.c b/util-linux/fdisk_osf.c
index ba01a7f0c..e281ea5d9 100644
--- a/util-linux/fdisk_osf.c
+++ b/util-linux/fdisk_osf.c
@@ -414,7 +414,7 @@ bsd_select(void)
                         break;
                 case 'q':
                         if (ENABLE_FEATURE_CLEAN_UP)
-                                close(dev_fd);
+                                close_dev_fd();
                         exit(EXIT_SUCCESS);
                 case 'r':
                         return;