libfdisk: (dos) make EBR parser more robust

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libfdisk/src/dos.c b/libfdisk/src/dos.c
index b1b23350fda0e24cf017632fcce84eb290a91bc4..5287c945da31976b73f56d1db858d266223a45bf 100644 (file)
--- a/libfdisk/src/dos.c
+++ b/libfdisk/src/dos.c
@@ -218,17 +218,23 @@ static int read_sector(struct fdisk_context *cxt, sector_t secno,
                        unsigned char *buf)
 {
        int rc = seek_sector(cxt, secno);
+       ssize_t r;
 
        if (rc < 0)
                return rc;
 
-       return read(cxt->dev_fd, buf, cxt->sector_size) !=
-                       (ssize_t) cxt->sector_size ? -errno : 0;
+       r = read(cxt->dev_fd, buf, cxt->sector_size);
+       if (r == (ssize_t) cxt->sector_size)
+               return 0;
+       if (r < 0)
+               return -errno;
+       return -1;
 }
 
 /* Allocate a buffer and read a partition table sector */
 static int read_pte(struct fdisk_context *cxt, size_t pno, sector_t offset)
 {
+       int rc;
        unsigned char *buf;
        struct pte *pe = self_pte(cxt, pno);
 
@@ -242,9 +248,13 @@ static int read_pte(struct fdisk_context *cxt, size_t pno, sector_t offset)
        pe->sectorbuffer = buf;
        pe->private_sectorbuffer = 1;
 
-       if (read_sector(cxt, offset, pe->sectorbuffer) != 0)
+       rc = read_sector(cxt, offset, pe->sectorbuffer);
+       if (rc) {
                fdisk_warn(cxt, _("Failed to read extended partition table "
                                "(offset=%ju)"), (uintmax_t) offset);
+               return rc;
+       }
+
        pe->changed = 0;
        pe->pt_entry = pe->ex_entry = NULL;
        return 0;
@@ -492,8 +502,9 @@ static void read_extended(struct fdisk_context *cxt, size_t ext)
                        return;
                }
 
-               read_pte(cxt, cxt->label->nparts_max,
-                        l->ext_offset + dos_partition_get_start(p));
+               if (read_pte(cxt, cxt->label->nparts_max, l->ext_offset +
+                                               dos_partition_get_start(p)))
+                       return;
 
                if (!l->ext_offset)
                        l->ext_offset = dos_partition_get_start(p);