CVE-2023-27477 (published 2023-03-08T21:15Z)

wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's code generation backend, Cranelift, has a bug on x86_64 platforms for the WebAssembly `i8x16.select` instruction which will produce the wrong results when the same operand is provided to the instruction and some of the selected indices are greater than 16. There is an off-by-one error in the calculation of the mask to the `pshufb` instruction which causes incorrect results to be returned if lanes are selected from the second vector. This codegen bug has been fixed in Wasmtiem 6.0.1, 5.0.1, and 4.0.1. Users are recommended to upgrade to these updated versions. If upgrading is not an option for you at this time, you can avoid this miscompilation by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other platforms such as AArch64 and s390x are not affected.

CVSS v3 base score: 4.3, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N)

Weakness information:
cwe_id: CWE-193
cwe_name: Off-by-one Error
description: A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
extended_description: 
            
            
            
            
            
         
         

Fix information:
repo_url: https://github.com/bytecodealliance/wasmtime
commit_details: repo_url: https://github.com/bytecodealliance/wasmtime
author: Alex Crichton
author_date: 2023-03-08 13:00:00-06:00
msg: Merge pull request from GHSA-xm67-587q-r2vw

This commit fixes an off-by-one error in the subtraction of indices when
shuffling a vector with itself. Lanes 16-and-above are mapped to select
from the first vector since the first and second element are the same,
but the subtraction was with 15 rather than 16 by accident.
repository: repo_url: https://github.com/bytecodealliance/wasmtime
repo_name: bytecodealliance/wasmtime
description: A fast and secure runtime for WebAssembly
repo_language: Rust
owner: bytecodealliance
file_changes: filename: isle.rs
change_type: ModificationType.MODIFY
diff: @@ -752,7 +752,7 @@ impl Context for IsleContext<'_, '_, MInst, X64Backend> {
     fn shuffle_0_31_mask(&mut self, mask: &VecMask) -> VCodeConstant {
         let mask = mask
             .iter()
-            .map(|&b| if b > 15 { b.wrapping_sub(15) } else { b })
+            .map(|&b| if b > 15 { b.wrapping_sub(16) } else { b })
             .map(|b| if b > 15 { 0b10000000 } else { b })
             .collect();
         self.lower_ctx

programming_language: Rust
filename: simd-lane-access-compile.clif
change_type: ModificationType.MODIFY
diff: @@ -101,7 +101,8 @@ block0:
 ;   addb %al, (%rax)
 ;   addb %al, (%rax)
 ;   addb %al, (%rax)
-;   addb %al, (%rcx, %rax)
+;   addb %al, (%rbx)
+;   addl %eax, (%rax)
 ;   addb %al, (%rax)
 ;   addb %al, (%rax)
 ;   addb %al, (%rax)

programming_language: Batchfile
filename: simd-shuffle.clif
change_type: ModificationType.MODIFY
diff: @@ -19,3 +19,10 @@ block0(v0: i8x16, v1: i8x16):
     return v2
 }
 ; run: %shuffle_zeros([1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16], [17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32]) == [4 1 0 0 5 7 13 12 24 14 25 5 3 0 18 6]
+
+function %shuffle1(i8x16) -> i8x16 {
+block0(v0: i8x16):
+    v1 = shuffle v0, v0, [8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23]
+    return v1
+}
+; run: %shuffle1([0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15]) == [8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7]

programming_language: Go