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Fail immediately when trying to write/erase wp regions

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This patch introduces chipset-level protections and adds checks that
abort writing to flash if any of the requested regions are
write-protected by chip, dynamically by a chipset, or are defined as
read-only.

This change is done so it's harder for user to brick his own platform.
Information about read-only regions can easily be missed as flashrom
can output a lot of information on screen. Even if you notice you might
not know if one of the regions you requested falls inside read-only
range, especially if using different names for those regions.
If you are flashing multiple regions or ones that partially overlap with
read-only parts then that could result in flashrom failing in the
middle leaving you in unknown state.

This patch was tested with multiple combinations of
unprotected/protected regions:

- dummy programmer

```sh
flashrom -p dummy:hwwp=yes,emulate=S25FL128L --wp-enable \
  --wp-range 0x00040000,0x00fc0000 \
  -l <(echo '00000000:0004ffff part1') -i part1 -E
```

- internal programmer on Protectli VP6670 with Dasharo UEFI firmware
with locked BIOS boot medium (PR0, part of bios region)

```sh
flashrom -p internal --ifd -i me -i bios -w test.rom
```

Normal reads and flashing non-protected regions was also tested.

Change-Id: Ia0dd847923e20ff0081ceae68984369e98952c2f
Signed-off-by: Michał Iwanicki <michal.iwanicki@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/89222
Reviewed-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
This commit is contained in:
Michał Iwanicki
2025-09-17 14:14:42 +02:00
committed by Anastasia Klimchuk
parent 45fc49e99b
commit 2a092bbef7
5 changed files with 154 additions and 12 deletions
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75
flashrom.c
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@@ -384,6 +384,22 @@ void get_flash_region(const struct flashctx *flash, int addr, struct flash_regio
}
}
void get_protected_ranges(const struct flashctx *flash, struct protected_ranges *ranges) {
if ((flash->mst->buses_supported & BUS_PROG) && flash->mst->opaque.get_protected_ranges) {
flash->mst->opaque.get_protected_ranges(ranges);
} else {
*ranges = (const struct protected_ranges){ 0 };
}
}
void release_protected_ranges(const struct flashctx *flash, struct protected_ranges *ranges) {
for (int i = 0; i < ranges->count; ++i) {
free(ranges->ranges[i].name);
}
free(ranges->ranges);
*ranges = (const struct protected_ranges){ 0 };
}
int check_for_unwritable_regions(const struct flashctx *flash, unsigned int start, unsigned int len)
{
struct flash_region region;
@@ -1817,6 +1833,58 @@ warn_out:
return ret;
}
static bool can_change_target_regions(struct flashctx *flash) {
bool check_wp = false;
size_t wp_start, wp_len;
enum flashrom_wp_mode mode;
struct flashrom_wp_cfg *cfg = NULL;
const struct romentry *entry = NULL;
const struct flashrom_layout *const layout = get_layout(flash);
struct protected_ranges ranges;
get_protected_ranges(flash, &ranges);
if (flashrom_wp_cfg_new(&cfg) == FLASHROM_WP_OK &&
flashrom_wp_read_cfg(cfg, flash) == FLASHROM_WP_OK)
{
flashrom_wp_get_range(&wp_start, &wp_len, cfg);
mode = flashrom_wp_get_mode(cfg);
if (mode != FLASHROM_WP_MODE_DISABLED && wp_len != 0)
check_wp = true;
}
flashrom_wp_cfg_release(cfg);
while ((entry = layout_next_included(layout, entry))) {
if (!flash->flags.skip_unwritable_regions &&
check_for_unwritable_regions(flash, entry->region.start,
entry->region.end - entry->region.start + 1))
{
release_protected_ranges(flash, &ranges);
return false;
}
if (check_wp && entry->region.start < wp_start + wp_len && wp_start <= entry->region.end) {
msg_gerr("%s: cannot fully update %s region (%#08"PRIx32"..%#08"PRIx32")"
" due to chip's write-protection.\n", __func__,
entry->region.name, entry->region.start, entry->region.end);
release_protected_ranges(flash, &ranges);
return false;
}
for (int i = 0; i < ranges.count; ++i) {
struct flash_region prot = ranges.ranges[i];
if (prot.write_prot && prot.start <= entry->region.end &&
prot.end >= entry->region.start) {
msg_gerr("%s: cannot fully update %s region (%#08"PRIx32"..%#08"PRIx32")"
" due to chipset write-protection.\n", __func__,
entry->region.name, entry->region.start, entry->region.end);
release_protected_ranges(flash, &ranges);
return false;
}
}
}
release_protected_ranges(flash, &ranges);
return true;
}
int prepare_flash_access(struct flashctx *const flash,
const bool read_it, const bool write_it,
const bool erase_it, const bool verify_it)
@@ -1831,6 +1899,13 @@ int prepare_flash_access(struct flashctx *const flash,
return 1;
}
if ((write_it || erase_it) && !flash->flags.force) {
if (!can_change_target_regions(flash)) {
msg_cerr("At least one target region is not fully writable. Aborting.\n");
return 1;
}
}
if (map_flash(flash) != 0)
return 1;