criu/log: properly handle truncated length from vsnprintf#2819
Merged
Conversation
avagin
marked this pull request as draft
November 11, 2025 23:18
vsnprintf does not always return the number of bytes actually written to the buffer. If the output was truncated due to the buffer limit, the return value is the total number of bytes which WOULD have been written to the final string if enough space had been available. This means we must cap the return value to the buffer size excluding the terminating null byte to correctly calculate the log entry size. Signed-off-by: Andrei Vagin <avagin@google.com>
avagin
force-pushed
the
criu-log-sprintf-ret
branch
from
November 11, 2025 23:21
d138c94 to
cdff770
Compare
avagin
marked this pull request as ready for review
November 11, 2025 23:41
There was a problem hiding this comment.
Pull Request Overview
Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
kolyshkin
reviewed
Nov 12, 2025
kolyshkin
left a comment
kolyshkin
left a comment
Contributor
There was a problem hiding this comment.
One more (minor) issue found.
Using sizeof(hdr) where hdr is a pointer gives the size of the pointer, not the size of the structure it points to. Reported-by: Kir Kolyshkin <kolyshkin@gmail.com> Signed-off-by: Andrei Vagin <avagin@gmail.com>
kolyshkin
approved these changes
Nov 12, 2025
This was referenced Nov 12, 2025
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
vsnprintf does not always return the number of bytes actually written to the buffer.
If the output was truncated due to the buffer limit, the return value is the total number of bytes which WOULD have been written to the final string if enough space had been available.
This means we must cap the return value to the buffer size excluding the terminating null byte to correctly calculate the log entry size.
Fixes #2781