fix(MPU): promote attr to uint32_t before shifting in ARM_MPU_SetMemAttrEx#305
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saikumar-mandaji wants to merge 1 commit into
Open
fix(MPU): promote attr to uint32_t before shifting in ARM_MPU_SetMemAttrEx#305saikumar-mandaji wants to merge 1 commit into
saikumar-mandaji wants to merge 1 commit into
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…ttrEx attr is uint8_t. In `attr << pos`, integer promotion converts attr to a signed int before the shift; for attr >= 0x80 and pos == 24 the mathematical result (up to 0xFF000000) exceeds INT_MAX, which is undefined behavior for a signed left shift, not merely implementation-defined truncation. Fix: promote attr to uint32_t explicitly before shifting, so the shift is performed in unsigned arithmetic and cannot overflow, matching the fix suggested in the issue. Fixes ARM-software#169 Signed-off-by: Saikumar Mandaji <mandajisaikumar@gmail.com>
Test Results 292 files - 352 292 suites - 352 0s ⏱️ - 15m 56s Results for commit b418536. ± Comparison against base commit 7f62ddc. This pull request removes 49 and adds 56 tests. Note that renamed tests count towards both.This pull request removes 5 skipped tests and adds 2 skipped tests. Note that renamed tests count towards both. |
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Fixes #169
Problem
ARM_MPU_SetMemAttrExcomputesattr << poswhereattrisuint8_t. Integer promotion convertsattrto a signedintbefore the shift is evaluated. Forattr >= 0x80andpos == 24, the mathematical result (up to0xFF000000) exceedsINT_MAX, which is undefined behavior for a signed left shift -- not merely implementation-defined truncation.Fix
Promote
attrtouint32_texplicitly before shifting, so the shift is performed in unsigned arithmetic and cannot overflow, matching the fix suggested in the issue.Verification
Verified by hand against the issue's analysis (integer-promotion rules for
E1 << E2, and the resulting range forattr << posatpos == 24). No C compiler was available in the environment this patch was authored in, so I was not able to build/run against the test suite directly -- please double-check against CI/local build before merging.