This fixes CVE-2018-18439 ("insufficient boundary checks in network image boot") by using lmb to check for a valid range to store received blocks.

Signed-off-by: Simon Goldschmidt simon.k.r.goldschmidt@gmail.com ---

Changes in v2: - this patch is new in v2

net/tftp.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 57 insertions(+), 9 deletions(-)

diff --git a/net/tftp.c b/net/tftp.c index 563ce3a06f..390394199d 100644 --- a/net/tftp.c +++ b/net/tftp.c @@ -17,6 +17,8 @@ #include <flash.h> #endif

+DECLARE_GLOBAL_DATA_PTR; + /* Well known TFTP port # */ #define WELL_KNOWN_PORT 69 /* Millisecs to timeout for lost pkt */ @@ -81,6 +83,8 @@ static ulong tftp_block_wrap; /* memory offset due to wrapping */ static ulong tftp_block_wrap_offset; static int tftp_state; +static ulong tftp_load_addr; +static ulong tftp_load_size; #ifdef CONFIG_TFTP_TSIZE /* The file size reported by the server */ static int tftp_tsize; @@ -134,10 +138,11 @@ static char tftp_filename[MAX_LEN]; static unsigned short tftp_block_size = TFTP_BLOCK_SIZE; static unsigned short tftp_block_size_option = TFTP_MTU_BLOCKSIZE;

-static inline void store_block(int block, uchar *src, unsigned len) +static inline int store_block(int block, uchar *src, unsigned int len) { ulong offset = block * tftp_block_size + tftp_block_wrap_offset; ulong newsize = offset + len; + ulong store_addr = tftp_load_addr + offset; #ifdef CONFIG_SYS_DIRECT_FLASH_TFTP int i, rc = 0;

@@ -145,30 +150,38 @@ static inline void store_block(int block, uchar *src, unsigned len) /* start address in flash? */ if (flash_info[i].flash_id == FLASH_UNKNOWN) continue; - if (load_addr + offset >= flash_info[i].start[0]) { + if (store_addr >= flash_info[i].start[0]) { rc = 1; break; } }

if (rc) { /* Flash is destination for this packet */ - rc = flash_write((char *)src, (ulong)(load_addr+offset), len); + rc = flash_write((char *)src, store_addr, len); if (rc) { flash_perror(rc); - net_set_state(NETLOOP_FAIL); - return; + return rc; } } else #endif /* CONFIG_SYS_DIRECT_FLASH_TFTP */ { - void *ptr = map_sysmem(load_addr + offset, len); + void *ptr;

+ if (store_addr < tftp_load_addr || + store_addr + len > tftp_load_addr + tftp_load_size) { + puts("\nTFTP error: "); + puts("trying to overwrite reserved memory...\n"); + return -1; + } + ptr = map_sysmem(store_addr, len); memcpy(ptr, src, len); unmap_sysmem(ptr); }

if (net_boot_file_size < newsize) net_boot_file_size = newsize; + + return 0; }

/* Clear our state ready for a new transfer */ @@ -527,7 +540,11 @@ static void tftp_handler(uchar *pkt, unsigned dest, struct in_addr sip, timeout_count_max = tftp_timeout_count_max; net_set_timeout_handler(timeout_ms, tftp_timeout_handler);

- store_block(tftp_cur_block - 1, pkt + 2, len); + if (store_block(tftp_cur_block - 1, pkt + 2, len)) { + eth_halt(); + net_set_state(NETLOOP_FAIL); + break; + }

/* * Acknowledge the block just received, which will prompt @@ -577,6 +594,24 @@ static void tftp_timeout_handler(void) } }

+/* Initialize tftp_load_addr and tftp_load_size from load_addr and lmb */ +static int tftp_init_load_addr(void) +{ + struct lmb lmb; + phys_size_t max_size; + + tftp_load_addr = load_addr; + + lmb_init_and_reserve(&lmb, gd->bd->bi_dram[0].start, + gd->bd->bi_dram[0].size, (void *)gd->fdt_blob); + + max_size = lmb_get_unreserved_size(&lmb, tftp_load_addr); + if (!max_size) + return -1; + + tftp_load_size = max_size; + return 0; +}

void tftp_start(enum proto_t protocol) { @@ -673,7 +708,14 @@ void tftp_start(enum proto_t protocol) } else #endif { - printf("Load address: 0x%lx\n", load_addr); + if (tftp_init_load_addr()) { + eth_halt(); + net_set_state(NETLOOP_FAIL); + puts("\nTFTP error: "); + puts("trying to overwrite reserved memory...\n"); + return; + } + printf("Load address: 0x%lx\n", tftp_load_addr); puts("Loading: *\b"); tftp_state = STATE_SEND_RRQ; #ifdef CONFIG_CMD_BOOTEFI @@ -721,9 +763,15 @@ void tftp_start_server(void) { tftp_filename[0] = 0;

+ if (tftp_init_load_addr()) { + eth_halt(); + net_set_state(NETLOOP_FAIL); + puts("\nTFTP error: trying to overwrite reserved memory...\n"); + return; + } printf("Using %s device\n", eth_get_name()); printf("Listening for TFTP transfer on %pI4\n", &net_ip); - printf("Load address: 0x%lx\n", load_addr); + printf("Load address: 0x%lx\n", tftp_load_addr);

puts("Loading: *\b");