kern: reply buffer capacity checking #1954
Open
Conversation
This file contains 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
The syscall docs say that attempting to reply with a message that's too big for your client to accept is a programming error. Programming errors are expected to produce faults in the program with the error. This fault is documented as being of type `ReplyTooLarge`. However, there is no such fault defined in the ABI, and the actual behavior of the kernel is to deliver the prefix of the reply that fits, and hand the client the length of that prefix. In our current world, this means the client will generally die shortly thereafter with a deserialization error. In a potential future world where messages can contain variable length portions, the client might not even hit an error when the reply is truncated. The code in the kernel has been marked with a TODO since forever. This commit resolves the TODO by adding a check and fault reason.
cbiffle
force-pushed
the
cbiffle/no-truncate-reply
branch
from
4200e2f to
c482f02
Compare
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Outdated suggestions cannot be applied.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.
The syscall docs say that attempting to reply with a message that's too big for your client to accept is a programming error. Programming errors are expected to produce faults in the program with the error. This fault is documented as being of type
ReplyTooLarge.However, there is no such fault defined in the ABI, and the actual behavior of the kernel is to deliver the prefix of the reply that fits, and hand the client the length of that prefix. In our current world, this means the client will generally die shortly thereafter with a deserialization error.
In a potential future world where messages can contain variable length portions, the client might not even hit an error when the reply is truncated.
The code in the kernel has been marked with a TODO since forever. This commit resolves the TODO by adding a check and fault reason.