Add another epicycle to -A processing that ensures ONLY the

partition table is changed. Not the GPT header. Not the MBR. And
only write back as much partition table information as the header
claims to have room for.

At a minimum should make -A safer when operating on the Apple M1
GPT.

A major overhaul of this code is urgently needed before someone
sneezes too hard in its vicinity.

Feedback kettenis@ & ok deraadt@

diff --git a/sbin/fdisk/cmd.c b/sbin/fdisk/cmd.c
index 777e48b..76701b1 100644 (file)
--- a/sbin/fdisk/cmd.c
+++ b/sbin/fdisk/cmd.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: cmd.c,v 1.117 2021/06/21 02:05:30 krw Exp $   */
+/*     $OpenBSD: cmd.c,v 1.118 2021/06/28 19:50:30 krw Exp $   */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -63,7 +63,7 @@ Xreinit(char *args, struct mbr *mbr)
 
        if (dogpt) {
                MBR_init_GPT(mbr);
-               GPT_init();
+               GPT_init(GHANDGP, 0);
                GPT_print("s", TERSE);
        } else {
                memset(&gh, 0, sizeof(gh));

diff --git a/sbin/fdisk/fdisk.c b/sbin/fdisk/fdisk.c
index b1f3870..59a43da 100644 (file)
--- a/sbin/fdisk/fdisk.c
+++ b/sbin/fdisk/fdisk.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: fdisk.c,v 1.113 2021/06/25 19:24:53 krw Exp $ */
+/*     $OpenBSD: fdisk.c,v 1.114 2021/06/28 19:50:30 krw Exp $ */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -222,14 +222,14 @@ main(int argc, char *argv[])
                if (letoh64(gh.gh_sig) != GPTSIGNATURE)
                        errx(1, "-A requires a valid GPT");
                else {
-                       MBR_init_GPT(&initial_mbr);
-                       GPT_init();
+                       initial_mbr = mbr;      /* Keep current MBR. */
+                       GPT_init(GPONLY, b_sectors);
                        query = "Do you wish to write new GPT?";
                }
        } else if (i_flag) {
                if (g_flag) {
                        MBR_init_GPT(&initial_mbr);
-                       GPT_init();
+                       GPT_init(GHANDGP, b_sectors);
                        query = "Do you wish to write new GPT?";
                } else {
                        memset(&gh, 0, sizeof(gh));

diff --git a/sbin/fdisk/gpt.c b/sbin/fdisk/gpt.c
index 83e5201..df8b0f2 100644 (file)
--- a/sbin/fdisk/gpt.c
+++ b/sbin/fdisk/gpt.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: gpt.c,v 1.33 2021/06/25 19:24:53 krw Exp $    */
+/*     $OpenBSD: gpt.c,v 1.34 2021/06/28 19:50:30 krw Exp $    */
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -49,7 +49,7 @@ int                     add_partition(const uint8_t *, const char *, uint64_t);
 int                      get_header(off_t);
 int                      get_partition_table(void);
 int                      init_gh(void);
-int                      init_gp(void);
+int                      init_gp(int, uint32_t);
 
 int
 get_header(off_t where)
@@ -413,17 +413,15 @@ init_gh(void)
 }
 
 int
-init_gp(void)
+init_gp(int how, uint32_t bootsectors)
 {
-       extern uint32_t b_sectors;
-       extern int A_flag;
        const uint8_t gpt_uuid_efi_system[] = GPT_UUID_EFI_SYSTEM;
        const uint8_t gpt_uuid_openbsd[] = GPT_UUID_OPENBSD;
        struct gpt_partition oldgp[NGPTPARTITIONS];
        int pn, rslt;
 
        memcpy(&oldgp, &gp, sizeof(oldgp));
-       if (A_flag == 0)
+       if (how == GHANDGP)
                memset(&gp, 0, sizeof(gp));
        else {
                for (pn = 0; pn < NGPTPARTITIONS; pn++) {
@@ -434,9 +432,9 @@ init_gp(void)
        }
 
        rslt = 0;
-       if (b_sectors > 0) {
+       if (bootsectors > 0) {
                rslt = add_partition(gpt_uuid_efi_system, "EFI System Area",
-                   b_sectors);
+                   bootsectors);
        }
        if (rslt == 0)
                rslt = add_partition(gpt_uuid_openbsd, "OpenBSD Area", 0);
@@ -448,13 +446,14 @@ init_gp(void)
 }
 
 int
-GPT_init(void)
+GPT_init(int how, uint32_t bootsectors)
 {
-       int rslt;
+       int rslt = 0;
 
-       rslt = init_gh();
+       if (how == GHANDGP)
+               rslt = init_gh();
        if (rslt == 0)
-               rslt = init_gp();
+               rslt = init_gp(how, bootsectors);
 
        return rslt;
 }
@@ -498,10 +497,9 @@ GPT_write(void)
        uint64_t altgh, altgp, prigh, prigp, gpbytes;
 
        /*
-        * XXX Assume we always write full-size partition table.
         * XXX Assume size of gp is multiple of sector size.
         */
-       gpbytes = sizeof(gp);
+       gpbytes = letoh64(gh.gh_part_num) * letoh64(gh.gh_part_size);
 
        prigh = GPTSECTOR;
        prigp = prigh + 1;

diff --git a/sbin/fdisk/gpt.h b/sbin/fdisk/gpt.h
index f349b81..69531c0 100644 (file)
--- a/sbin/fdisk/gpt.h
+++ b/sbin/fdisk/gpt.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: gpt.h,v 1.12 2021/06/16 15:40:47 krw Exp $    */
+/*     $OpenBSD: gpt.h,v 1.13 2021/06/28 19:50:30 krw Exp $    */
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -20,7 +20,7 @@ void          GPT_read(int);
 int            GPT_get_lba_start(unsigned int);
 int            GPT_get_lba_end(unsigned int);
 
-int            GPT_init(void);
+int            GPT_init(int, uint32_t);
 int            GPT_write(void);
 void           GPT_zap_headers(void);
 void           GPT_print(char *, int);
@@ -36,3 +36,6 @@ extern struct gpt_partition gp[NGPTPARTITIONS];
 
 #define        TERSE           0
 #define        VERBOSE         1
+
+#define        GHANDGP         0
+#define        GPONLY          1