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rseq: Remove broken uapi field layout on 32-bit little endian
[ Upstream commitbfdf4e6208
] The rseq rseq_cs.ptr.{ptr32,padding} uapi endianness handling is entirely wrong on 32-bit little endian: a preprocessor logic mistake wrongly uses the big endian field layout on 32-bit little endian architectures. Fortunately, those ptr32 accessors were never used within the kernel, and only meant as a convenience for user-space. Remove those and replace the whole rseq_cs union by a __u64 type, as this is the only thing really needed to express the ABI. Document how 32-bit architectures are meant to interact with this field. Fixes:ec9c82e03a
("rseq: uapi: Declare rseq_cs field as union, update includes") Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220127152720.25898-1-mathieu.desnoyers@efficios.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -105,23 +105,11 @@ struct rseq {
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* Read and set by the kernel. Set by user-space with single-copy
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* atomicity semantics. This field should only be updated by the
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* thread which registered this data structure. Aligned on 64-bit.
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*
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* 32-bit architectures should update the low order bits of the
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* rseq_cs field, leaving the high order bits initialized to 0.
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*/
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union {
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__u64 ptr64;
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#ifdef __LP64__
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__u64 ptr;
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#else
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struct {
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#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)
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__u32 padding; /* Initialized to zero. */
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__u32 ptr32;
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#else /* LITTLE */
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__u32 ptr32;
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__u32 padding; /* Initialized to zero. */
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#endif /* ENDIAN */
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} ptr;
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#endif
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} rseq_cs;
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__u64 rseq_cs;
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/*
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* Restartable sequences flags field.
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@ -128,10 +128,10 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
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int ret;
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#ifdef CONFIG_64BIT
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if (get_user(ptr, &t->rseq->rseq_cs.ptr64))
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if (get_user(ptr, &t->rseq->rseq_cs))
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return -EFAULT;
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#else
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if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr)))
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if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr)))
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return -EFAULT;
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#endif
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if (!ptr) {
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@ -217,9 +217,9 @@ static int clear_rseq_cs(struct task_struct *t)
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* Set rseq_cs to NULL.
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*/
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#ifdef CONFIG_64BIT
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return put_user(0UL, &t->rseq->rseq_cs.ptr64);
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return put_user(0UL, &t->rseq->rseq_cs);
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#else
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if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64)))
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if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs)))
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return -EFAULT;
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return 0;
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#endif
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