Commit fbd2267e authored by Thomas Altenbach's avatar Thomas Altenbach Committed by Jamie
Browse files

boot: bootutil: Fix invalid last sector computation for swap-scratch 



At the beginning of a swap-scratch upgrade, the index of the last sector
in the primary slot that need to be swapped is computed using the
'find_last_sector_idx' routine. However, if the primary slot is composed
of larger sectors than the secondary slots, this routine could return a
wrong sector index for the primary slot. The index might even be outside
the primary slot, which would lead to (at best) a simple failure of the
upgrade and at worst a corruption of the flash memory bricking the
device.

This commit fixes the issue by ensuring 'find_last_sector_idx' always
returns a valid sector index for the primary slot.

Signed-off-by: default avatarThomas Altenbach <thomas.altenbach@legrand.com>
parent 7724bcfd

boot/bootutil/src/swap_scratch.c

+9 −6
Original line number Diff line number Diff line
@@ -464,13 +464,15 @@ boot_copy_sz(const struct boot_loader_state *state, int last_sector_idx, 
static int

find_last_sector_idx(const struct boot_loader_state *state, uint32_t copy_size)

{

    int last_sector_idx;

    int last_sector_idx_primary;

    int last_sector_idx_secondary;

    uint32_t primary_slot_size;

    uint32_t secondary_slot_size;



    primary_slot_size = 0;

    secondary_slot_size = 0;

    last_sector_idx = 0;

    last_sector_idx_primary = 0;

    last_sector_idx_secondary = 0;



    /*

     * Knowing the size of the largest image between both slots, here we
@@ -483,23 +485,24 @@ find_last_sector_idx(const struct boot_loader_state *state, uint32_t copy_size) 
            (primary_slot_size < secondary_slot_size)) {

           primary_slot_size += boot_img_sector_size(state,

                                                     BOOT_PRIMARY_SLOT,

                                                     last_sector_idx);

                                                     last_sector_idx_primary);

            ++last_sector_idx_primary;

        }

        if ((secondary_slot_size < copy_size) ||

            (secondary_slot_size < primary_slot_size)) {

           secondary_slot_size += boot_img_sector_size(state,

                                                       BOOT_SECONDARY_SLOT,

                                                       last_sector_idx);

                                                       last_sector_idx_secondary);

            ++last_sector_idx_secondary;

        }

        if (primary_slot_size >= copy_size &&

                secondary_slot_size >= copy_size &&

                primary_slot_size == secondary_slot_size) {

            break;

        }

        last_sector_idx++;

    }



    return last_sector_idx;

    return last_sector_idx_primary - 1;

}



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