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pkt-line: do not scan past NUL on empty packet in find_packfile_uri_path - #2472
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When packet_read_with_status() reads an empty data packet ("0004") while
PACKET_READ_REDACT_URI_PATH is enabled, it sets buffer[0] = 0 and calls
find_packfile_uri_path(buffer).
Because find_packfile_uri_path() unconditionally advances buffer by 1 to
skip the sideband byte before scanning for a hex object ID and URI, an
empty packet causes it to step past the NUL terminator at buffer[0] into
unwritten or stale bytes left in buffer[1..] from a previous packet. If
the previous packet in packet_buffer contained a packfile-uri line,
find_packfile_uri_path() matches the stale URI and returns a pointer at
a positive offset, causing strbuf_splice(&tracebuf, ...) on the 0-length
tracebuf to fail with:
BUG: strbuf.c: 'pos' is too far after the end of the buffer
Check that buffer is non-empty (!*buffer) before skipping the sideband
byte in find_packfile_uri_path().
Found via agent swarm driven property tests using
https://recursion.wtf/posts/agents-and-property-tests/
Signed-off-by: Inanna Malick <inanna@recursion.wtf>
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moved this to Todo
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🟡 Changes recommended
A regression test is still needed for a sideband-prefixed packfile URI followed by an empty data packet with URI redaction enabled, since existing tests would not catch removal of the guard against the strbuf_splice() BUG.
1 open issue
What changed in this PR
This PR fixes empty-packet handling in packet-line URI redaction, preventing stale buffer contents from causing an abort.
Changes:
- Return early from
find_packfile_uri_path()when the buffer is empty. - Preserve URI scanning for nonempty packets.
| File | Description |
|---|---|
pkt-line.c |
Adds an empty-buffer guard before skipping the sideband byte. |
Review effort: Balanced
| if (!*buffer) | ||
| return NULL; |
|
/allow |
|
User inanna-malick is now allowed to use GitGitGadget. |
When
packet_read_with_status()reads an empty data packet ("0004") whilePACKET_READ_REDACT_URI_PATHis enabled, it setsbuffer[0] = 0and callsfind_packfile_uri_path(buffer).Because
find_packfile_uri_path()unconditionally advancesbufferby 1 to skip the sideband byte before scanning for a hex object ID and URI, an empty packet causes it to step past the NUL terminator atbuffer[0]into unwritten or stale bytes left inbuffer[1..]from a previous packet. If the previous packet inpacket_buffercontained apackfile-urisentry,find_packfile_uri_path()matches the stale URI and returns a pointer at a positive offset, causingstrbuf_splice(&tracebuf, ...)on the 0-lengthtracebufto abort with:Check that
bufferis non-empty (!*buffer) before skipping the sideband byte infind_packfile_uri_path().Found via agent swarm driven property tests using https://recursion.wtf/posts/agents-and-property-tests/