sched_setaffinity: Validate user memory before reading CPU mask#2145
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francescolavra merged 1 commit intomasterfrom Mar 9, 2026
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sched_setaffinity: Validate user memory before reading CPU mask#2145francescolavra merged 1 commit intomasterfrom
francescolavra merged 1 commit intomasterfrom
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niklasfemerstrand
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Mar 3, 2026
If the CPU mask pointer supplied as argument to sched_setaffinity() is not verified to belong to user memory, a program could pass an arbitrary address and determine from the syscall return value whether that address is mapped as kernel memory, thus defeating KASLR. Add a call to validate_user_memory() before accessing the CPU mask pointer, and to avoid a double validation replace the copy_from_user() call with a direct memory copy.
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If the CPU mask pointer supplied as argument to sched_setaffinity() is not verified to belong to user memory, a program could pass an arbitrary address and determine from the syscall return value whether that address is mapped as kernel memory, thus defeating KASLR.
Add a call to validate_user_memory() before accessing the CPU mask pointer, and to avoid a double validation replace the copy_from_user() call with a direct memory copy.
Issue reported and fix suggested by Niklas Femerstrand (@niklasfemerstrand).