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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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6d04fe15f7
For architectures like x86 and arm64 we don't need the separate bit to indicate that a pointer is a kernel pointer as the address spaces are unified. That way the sockptr_t can be reduced to a union of two pointers, which leads to nicer calling conventions. The only caveat is that we need to check that users don't pass in kernel address and thus gain access to kernel memory. Thus the USER_SOCKPTR helper is replaced with a init_user_sockptr function that does this check and returns an error if it fails. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: David S. Miller <davem@davemloft.net>
132 lines
2.8 KiB
C
132 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (c) 2020 Christoph Hellwig.
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*
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* Support for "universal" pointers that can point to either kernel or userspace
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* memory.
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*/
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#ifndef _LINUX_SOCKPTR_H
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#define _LINUX_SOCKPTR_H
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#include <linux/compiler.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
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typedef union {
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void *kernel;
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void __user *user;
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} sockptr_t;
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static inline bool sockptr_is_kernel(sockptr_t sockptr)
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{
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return (unsigned long)sockptr.kernel >= TASK_SIZE;
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}
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static inline sockptr_t KERNEL_SOCKPTR(void *p)
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{
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return (sockptr_t) { .kernel = p };
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}
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static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
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{
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if ((unsigned long)p >= TASK_SIZE)
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return -EFAULT;
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sp->user = p;
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return 0;
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}
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#else /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
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typedef struct {
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union {
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void *kernel;
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void __user *user;
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};
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bool is_kernel : 1;
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} sockptr_t;
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static inline bool sockptr_is_kernel(sockptr_t sockptr)
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{
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return sockptr.is_kernel;
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}
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static inline sockptr_t KERNEL_SOCKPTR(void *p)
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{
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return (sockptr_t) { .kernel = p, .is_kernel = true };
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}
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static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
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{
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sp->user = p;
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sp->is_kernel = false;
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return 0;
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}
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#endif /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
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static inline bool sockptr_is_null(sockptr_t sockptr)
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{
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return !sockptr.user && !sockptr.kernel;
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}
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static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
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{
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if (!sockptr_is_kernel(src))
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return copy_from_user(dst, src.user, size);
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memcpy(dst, src.kernel, size);
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return 0;
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}
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static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
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{
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if (!sockptr_is_kernel(dst))
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return copy_to_user(dst.user, src, size);
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memcpy(dst.kernel, src, size);
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return 0;
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}
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static inline void *memdup_sockptr(sockptr_t src, size_t len)
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{
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void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
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if (!p)
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return ERR_PTR(-ENOMEM);
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if (copy_from_sockptr(p, src, len)) {
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kfree(p);
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return ERR_PTR(-EFAULT);
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}
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return p;
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}
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static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
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{
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char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
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if (!p)
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return ERR_PTR(-ENOMEM);
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if (copy_from_sockptr(p, src, len)) {
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kfree(p);
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return ERR_PTR(-EFAULT);
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}
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p[len] = '\0';
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return p;
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}
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static inline void sockptr_advance(sockptr_t sockptr, size_t len)
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{
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if (sockptr_is_kernel(sockptr))
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sockptr.kernel += len;
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else
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sockptr.user += len;
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}
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static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
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{
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if (sockptr_is_kernel(src)) {
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size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
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memcpy(dst, src.kernel, len);
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return len;
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}
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return strncpy_from_user(dst, src.user, count);
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}
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#endif /* _LINUX_SOCKPTR_H */
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