[release/6.0] Port #58410: Fix zero initialization use of "initReg" #62207
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
…Reg" If the only local is an enregistered must-init struct, we were setting `initReg` to its register (in this case, `xmm0`). However, `initReg` is expected to be an integer register. In the test case, with GS cookie stress, the GS cookie code asserted that `initReg` was an integer register, but it wasn't. The fix is the change the condition to use the actual register assigned to the variable (in this case, `xmm0`), not the variable type (here, `TYP_STRUCT`). No spmi asm diffs. Fixes dotnet#57911
dotnet-issue-labeler
bot
added
the
area-CodeGen-coreclr
|
Tagging subscribers to this area: @JulieLeeMSFT Issue DetailsBackport #58410 to release/6.0 Customer ImpactSilent bad codegen: in certain rare cases, a variable is not correctly zero initialized, possibly leading to incorrect results or crashes. The issue was originally found with internal "stress" testing, but was reported by an external F# customer on the 6.0 release. TestingThe fix has been in 'main' for 3 months, but wasn't ported to release/6.0 before release. RiskLow
|
|
@jakobbotsch @dotnet/jit-contrib PTAL: back-port of fix to .NET 6 |
AndyAyersMS
approved these changes
Nov 30, 2021
jakobbotsch
approved these changes
Nov 30, 2021
jeffschwMSFT
approved these changes
Dec 1, 2021
Pilchie
added
Servicing-approved
ghost
locked as resolved and limited conversation to collaborators
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
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Outdated suggestions cannot be applied.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.
Backport #58410 to release/6.0
Fixes #62103
Customer Impact
Silent bad codegen: in certain rare cases, a variable is not correctly zero initialized, possibly leading to incorrect results or crashes. Typically, this requires a single local variable that is a register-sized struct, marked as requiring zero initialization by the JIT.
The issue was originally found with internal "stress" testing late in .NET 6 product development, but the fix was not ported to the .NET 6 release branch. However, it was subsequently reported by an external F# customer on the 6.0 release.
This was a regression between .NET 5 and .NET 6 due to extensive struct optimization work in the JIT.
Testing
The fix has been in 'main' for 3 months, but wasn't ported to release/6.0 before release.
Risk
Low