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GCS_MAVLink: list an entry which exactly fills a listing packet

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An entry needing exactly as many bytes as the payload holds was treated as
unsendable and dropped. It does fit: AP_HAL::Util::vsnprintf builds its
BufferPrinter with size-1 and then writes the terminator itself at
str[size-1], and the byte that overwrites is the entry's own trailing NUL,
so the encoding which lands in the buffer is the one intended.

Compare against the size rather than allowing it, in all three places, so
the two packing loops still agree on what can never be sent.
This commit is contained in:
Peter Barker
2026-09-12 15:00:50 +10:00
committed by Andrew Tridgell
parent b4697f8189
commit 4cedc1e346
1 changed files with 6 additions and 7 deletions
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libraries/GCS_MAVLink/GCS_FTP.cpp
+6 -7
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@@ -245,11 +245,10 @@ void GCS_FTP::Session::list_dir(Transaction &request, Transaction &response)
// check how much space would be needed to emit the listing
const int needed_space = gen_dir_entry((char *)response.data, sizeof(request.data), (char *)request.data, entry);
// an entry needing the whole packet still does not fit, as the
// packing loop below only takes an entry which leaves the index
// inside the buffer. both loops must agree on which entries are
// skipped or the offsets they are counting drift apart
if (needed_space < 0 || needed_space >= (int)sizeof(request.data)) {
// an entry needing more than a whole packet can never be sent. both
// loops must agree on which entries are skipped or the offsets they
// are counting drift apart
if (needed_space < 0 || needed_space > (int)sizeof(request.data)) {
continue;
}
@@ -272,12 +271,12 @@ void GCS_FTP::Session::list_dir(Transaction &request, Transaction &response)
// will be able to send it either. dropping it loses one file from
// the listing; breaking here would end the listing at an EndOfFile
// and lose every file after it as well
if (required_space >= (int)sizeof(response.data)) {
if (required_space > (int)sizeof(response.data)) {
continue;
}
// can't fit it in this one, leave it for the next list to send
if ((required_space + index) >= (int)sizeof(request.data)) {
if ((required_space + index) > (int)sizeof(request.data)) {
break;
}