mpk: protect memory with PROT_NONE#7363
Merged
abrown merged 1 commit intobytecodealliance:mainfrom Oct 25, 2023
Merged
Conversation
This change fixes a bug with `ProtectionKey::protect`: previously it initialized each stripe with read and write permissions (i.e., `pkey_mprotect(..., PROT_READ | PROT_WRITE)` under the mistaken assumption that these permissions were MPK-specific, "what MPK permissions will we be allowed to set in the PKRU for these regions in the future?". This assumption is incorrect: the regions were immediately made accessible for reading and writing. The fix is to initially protect the regions with `PROT_NONE` and allow Wasmtime's `memory.grow` implementation to mark pages with `mprotect(..., PROT_READ | PROT_WRITE)` as usual. Whether a store can access a slice is still determined by the CPU state set in `mpk::allow`.
alexcrichton
requested review from
alexcrichton
and removed request for
pchickey
alexcrichton
approved these changes
Oct 25, 2023
Member
alexcrichton
left a comment
alexcrichton
left a comment
There was a problem hiding this comment.
Nice! Is it possible to have a test in this regard? For example if mpk is enabled does that mean that guard pages were accidentally read/write?
Member
Author
|
Yes, I'm working on a test to push soon. The spec tests caught this accidental read/write once I was able to actually run them. |
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
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
This change fixes a bug with
ProtectionKey::protect: previously it initialized each stripe with read and write permissions (i.e.,pkey_mprotect(..., PROT_READ | PROT_WRITE)under the mistaken assumption that these permissions were MPK-specific, "what MPK permissions will we be allowed to set in the PKRU for these regions in the future?". This assumption is incorrect: the regions were immediately made accessible for reading and writing. The fix is to initially protect the regions withPROT_NONEand allow Wasmtime'smemory.growimplementation to mark pages withmprotect(..., PROT_READ | PROT_WRITE)as usual. Whether a store can access a slice is still determined by the CPU state set inmpk::allow.