From 7c643ed2855058657798d9e8e80701023de14a08 Mon Sep 17 00:00:00 2001 From: Karel Zak Date: Wed, 17 Jul 2019 12:11:38 +0200 Subject: libfdisk: don't use FAT as MBR The current libfdisk MBR detection is too weak, the result is that it reuses MBR from FAT. The correct behavior is to create a new MBR, wipe first sector (on write) and warn about obsolete FAT superblock. Reported-by: Mike Fleetwood Signed-off-by: Karel Zak --- libfdisk/src/context.c | 16 +++++++++++----- libfdisk/src/dos.c | 4 ++++ 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/libfdisk/src/context.c b/libfdisk/src/context.c index 770aa4d52..bc284f34e 100644 --- a/libfdisk/src/context.c +++ b/libfdisk/src/context.c @@ -619,14 +619,20 @@ static int fdisk_assign_fd(struct fdisk_context *cxt, int fd, if (fdisk_read_firstsector(cxt) < 0) goto fail; + /* warn about obsolete stuff on the device if we aren't in list-only */ + if (!fdisk_is_listonly(cxt) && fdisk_check_collisions(cxt) < 0) + goto fail; + fdisk_probe_labels(cxt); fdisk_apply_label_device_properties(cxt); - /* warn about obsolete stuff on the device if we aren't in - * list-only mode and there is not PT yet */ - if (!fdisk_is_listonly(cxt) && !fdisk_has_label(cxt) - && fdisk_check_collisions(cxt) < 0) - goto fail; + /* Don't report collision if there is already a valid partition table. + * The bootbits are wiped when we create a *new* partition table only. */ + if (fdisk_is_ptcollision(cxt) && fdisk_has_label(cxt)) { + cxt->pt_collision = 0; + free(cxt->collision); + cxt->collision = NULL; + } DBG(CXT, ul_debugobj(cxt, "initialized for %s [%s]", fname, readonly ? "READ-ONLY" : "READ-WRITE")); diff --git a/libfdisk/src/dos.c b/libfdisk/src/dos.c index 6dc276e8a..bd964db15 100644 --- a/libfdisk/src/dos.c +++ b/libfdisk/src/dos.c @@ -814,6 +814,10 @@ static int dos_probe_label(struct fdisk_context *cxt) if (!mbr_is_valid_magic(cxt->firstsector)) return 0; + /* ignore disks with FAT */ + if (cxt->collision && strcmp(cxt->collision, "vfat") == 0) + return 0; + dos_init(cxt); get_partition_table_geometry(cxt, &h, &s); -- cgit v1.2.3-55-g7522