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net: tftp: sanitize tftp block size, especially for TX

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U-Boot does not support IP fragmentation on TX (and unless
CONFIG_IP_DEFRAG is set, neither on RX). So the blocks we send must
fit in a single ethernet packet.

Currently, if tftpblocksize is set to something like 5000 and I
tftpput a large enough file, U-Boot crashes because we overflow
net_tx_packet (which only has room for 1500 bytes plus change).

Similarly, if tftpblocksize is set to something larger than what we
can actually receive (e.g. 50000, with NET_MAXDEFRAG being 16384), any
tftp get just hangs because we never receive any packets.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
This commit is contained in:
Rasmus Villemoes 2022-10-14 19:43:42 +02:00 committed by Tom Rini
parent 4b8c44e39c
commit 087648b5df
1 changed files with 47 additions and 0 deletions
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47
net/tftp.c
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@ -708,9 +708,54 @@ static int tftp_init_load_addr(void)
return 0;
}
static int saved_tftp_block_size_option;
static void sanitize_tftp_block_size_option(enum proto_t protocol)
{
int cap, max_defrag;
switch (protocol) {
case TFTPGET:
max_defrag = config_opt_enabled(CONFIG_IP_DEFRAG, CONFIG_NET_MAXDEFRAG, 0);
if (max_defrag) {
/* Account for IP, UDP and TFTP headers. */
cap = max_defrag - (20 + 8 + 4);
/* RFC2348 sets a hard upper limit. */
cap = min(cap, 65464);
break;
}
/*
* If not CONFIG_IP_DEFRAG, cap at the same value as
* for tftp put, namely normal MTU minus protocol
* overhead.
*/
fallthrough;
case TFTPPUT:
default:
/*
* U-Boot does not support IP fragmentation on TX, so
* this must be small enough that it fits normal MTU
* (and small enough that it fits net_tx_packet which
* has room for PKTSIZE_ALIGN bytes).
*/
cap = 1468;
}
if (tftp_block_size_option > cap) {
printf("Capping tftp block size option to %d (was %d)\n",
cap, tftp_block_size_option);
saved_tftp_block_size_option = tftp_block_size_option;
tftp_block_size_option = cap;
}
}
void tftp_start(enum proto_t protocol)
{
__maybe_unused char *ep; /* Environment pointer */
if (saved_tftp_block_size_option) {
tftp_block_size_option = saved_tftp_block_size_option;
saved_tftp_block_size_option = 0;
}
if (IS_ENABLED(CONFIG_NET_TFTP_VARS)) {
/*
@ -747,6 +792,8 @@ void tftp_start(enum proto_t protocol)
}
}
sanitize_tftp_block_size_option(protocol);
debug("TFTP blocksize = %i, TFTP windowsize = %d timeout = %ld ms\n",
tftp_block_size_option, tftp_window_size_option, timeout_ms);