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Fix two UAF errors in read_ihex_chunks() #554

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merged 1 commit into from
Sep 19, 2025
Merged

Fix two UAF errors in read_ihex_chunks() #554

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18 changes: 13 additions & 5 deletions simavr/sim/sim_hex.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,7 @@ read_ihex_chunks(
fw_chunk_t ** chunks_p )
{
fw_chunk_t *chunk = *chunks_p;
fw_chunk_t *backlink_p = chunk;
int len, allocation = 0;
uint8_t chk = 0;
uint8_t bline[272];
Expand Down Expand Up @@ -150,7 +151,7 @@ read_ihex_chunks(
}
if (!chunk || (chunk->size && addr != chunk->addr + chunk->size)) {
/* New chunk. */

backlink_p = chunk;
allocation = ALLOCATION - sizeof *chunk + 1;
chunk = (fw_chunk_t *)malloc(ALLOCATION);
*chunks_p = chunk;
Expand All @@ -170,6 +171,12 @@ read_ihex_chunks(

allocation += INCREMENT;
chunk = realloc(chunk, allocation + (sizeof *chunk - 1));

/* Update the pointer in the previous list element */
if ( backlink_p ) backlink_p->next = chunk;

/* Refresh the pointer to the future chunk */
chunks_p = &chunk->next;
}
memcpy(chunk->data + chunk->size, bline + 4, bline[0]);
chunk->size += bline[0];
Expand All @@ -178,7 +185,6 @@ read_ihex_chunks(
fclose(f);
}


uint8_t *
read_ihex_file(
const char * fname, uint32_t * dsize, uint32_t * start)
Expand Down Expand Up @@ -255,10 +261,10 @@ sim_setup_firmware(const char * filename, uint32_t loadBase,
}

#ifdef IHEX_TEST
// gcc -std=gnu99 -Isimavr/sim simavr/sim/sim_hex.c -o sim_hex -DIHEX_TEST -Dtest_main=main
// gcc -std=gnu99 -Isimavr/sim simavr/sim/sim_hex.c -o sim_hex -DIHEX_TEST -Dtest_main=main -fsanitize=address -fno-omit-frame-pointer -O1 -g
int test_main(int argc, char * argv[])
{
fw_chunk_t *chunks;
fw_chunk_t *chunks, *next_chunk;
int fi;

for (fi = 1; fi < argc; fi++) {
Expand All @@ -274,7 +280,9 @@ int test_main(int argc, char * argv[])
snprintf(n, sizeof n, "%s[%d] = %08x",
argv[fi], ci, chunks->addr);
hdump(n, chunks->data, chunks->size);
chunks = chunks->next;
next_chunk = chunks->next;
free(chunks);
chunks = next_chunk;
}
}
return 0;
Expand Down
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