From: Andrew Goodbody Date: Wed, 14 Jan 2026 15:12:09 +0000 (+0000) Subject: net: lwip: tftp: Do not write past buffer end X-Git-Tag: v2026.04-rc2~23^2~9 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8df6b78746ee1f4f0bb750aec9c4da2fb31d3e33;p=thirdparty%2Fu-boot.git net: lwip: tftp: Do not write past buffer end sprintf will add a trailing \0 so manually adding a trailing \0 will result in an extra unaccounted for character being written. This overwrote the first byte of the following allocation block resulting in unexpected behavior. This was found by Running 'pxe get' with no available file resulting in multiple attempts, using the default algorithm, to attempt to find a file. Eventually there would be a failed assert when free() was called. Failing the assert would result in a system reset. Fixes: 27d7ccda94fa ("net: lwip: tftp: add support of blksize option to client") Reported-by: Michal Simek Tested-by: Michal Simek Signed-off-by: Andrew Goodbody Tested-by: Tom Rini # Pine64+ Reviewed-by: Jerome Forissier Reviewed-by: Jerome Forissier --- diff --git a/lib/lwip/lwip/src/apps/tftp/tftp.c b/lib/lwip/lwip/src/apps/tftp/tftp.c index ecb6c55ae11..25da952e925 100644 --- a/lib/lwip/lwip/src/apps/tftp/tftp.c +++ b/lib/lwip/lwip/src/apps/tftp/tftp.c @@ -191,7 +191,7 @@ send_request(const ip_addr_t *addr, u16_t port, u16_t opcode, const char* fname, MEMCPY(payload+2, fname, fname_length); MEMCPY(payload+2+fname_length, mode, mode_length); if (tftp_state.blksize) - sprintf(payload+2+fname_length+mode_length, "blksize%c%d%c", 0, tftp_state.blksize, 0); + sprintf(payload+2+fname_length+mode_length, "blksize%c%d", 0, tftp_state.blksize); tftp_state.wait_oack = true; ret = udp_sendto(tftp_state.upcb, p, addr, port);