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c576eddf1c
Right now several architectures allow their set_memory_*() family of
functions to fail, but callers may not be checking the return values.
If set_memory_*() returns with an error, call-site assumptions may be
infact wrong to assume that it would either succeed or not succeed at
all. Ideally, the failure of set_memory_*() should be passed up the call
stack, and callers should examine the failure and deal with it.
Need to fix the callers and add the __must_check attribute. They also
may not provide any level of atomicity, in the sense that the memory
protections may be left incomplete on failure. This issue likely has a
few steps on effects architectures:
1) Have all callers of set_memory_*() helpers check the return value.
2) Add __must_check to all set_memory_*() helpers so that new uses do
not ignore the return value.
3) Add atomicity to the calls so that the memory protections aren't
left in a partial state.
This series is part of step 1. Make sram driver check the return value
of set_memory_*().
Signed-off-by: Tianlin Li <tli@digitalocean.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20191217194528.16461-1-tli@digitalocean.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
133 lines
3.8 KiB
C
133 lines
3.8 KiB
C
/*
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* SRAM protect-exec region helper functions
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*
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* Copyright (C) 2017 Texas Instruments Incorporated - http://www.ti.com/
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* Dave Gerlach
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed "as is" WITHOUT ANY WARRANTY of any
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* kind, whether express or implied; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/device.h>
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#include <linux/genalloc.h>
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#include <linux/mm.h>
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#include <linux/sram.h>
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#include <asm/fncpy.h>
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#include <asm/set_memory.h>
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#include "sram.h"
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static DEFINE_MUTEX(exec_pool_list_mutex);
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static LIST_HEAD(exec_pool_list);
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int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,
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struct sram_partition *part)
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{
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unsigned long base = (unsigned long)part->base;
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unsigned long end = base + block->size;
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if (!PAGE_ALIGNED(base) || !PAGE_ALIGNED(end)) {
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dev_err(sram->dev,
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"SRAM pool marked with 'protect-exec' is not page aligned and will not be created.\n");
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return -ENOMEM;
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}
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return 0;
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}
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int sram_add_protect_exec(struct sram_partition *part)
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{
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mutex_lock(&exec_pool_list_mutex);
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list_add_tail(&part->list, &exec_pool_list);
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mutex_unlock(&exec_pool_list_mutex);
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return 0;
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}
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/**
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* sram_exec_copy - copy data to a protected executable region of sram
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*
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* @pool: struct gen_pool retrieved that is part of this sram
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* @dst: Destination address for the copy, that must be inside pool
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* @src: Source address for the data to copy
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* @size: Size of copy to perform, which starting from dst, must reside in pool
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*
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* Return: Address for copied data that can safely be called through function
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* pointer, or NULL if problem.
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*
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* This helper function allows sram driver to act as central control location
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* of 'protect-exec' pools which are normal sram pools but are always set
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* read-only and executable except when copying data to them, at which point
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* they are set to read-write non-executable, to make sure no memory is
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* writeable and executable at the same time. This region must be page-aligned
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* and is checked during probe, otherwise page attribute manipulation would
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* not be possible. Care must be taken to only call the returned address as
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* dst address is not guaranteed to be safely callable.
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*
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* NOTE: This function uses the fncpy macro to move code to the executable
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* region. Some architectures have strict requirements for relocating
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* executable code, so fncpy is a macro that must be defined by any arch
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* making use of this functionality that guarantees a safe copy of exec
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* data and returns a safe address that can be called as a C function
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* pointer.
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*/
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void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src,
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size_t size)
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{
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struct sram_partition *part = NULL, *p;
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unsigned long base;
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int pages;
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void *dst_cpy;
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int ret;
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mutex_lock(&exec_pool_list_mutex);
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list_for_each_entry(p, &exec_pool_list, list) {
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if (p->pool == pool)
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part = p;
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}
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mutex_unlock(&exec_pool_list_mutex);
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if (!part)
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return NULL;
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if (!gen_pool_has_addr(pool, (unsigned long)dst, size))
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return NULL;
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base = (unsigned long)part->base;
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pages = PAGE_ALIGN(size) / PAGE_SIZE;
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mutex_lock(&part->lock);
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ret = set_memory_nx((unsigned long)base, pages);
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if (ret)
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goto error_out;
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ret = set_memory_rw((unsigned long)base, pages);
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if (ret)
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goto error_out;
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dst_cpy = fncpy(dst, src, size);
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ret = set_memory_ro((unsigned long)base, pages);
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if (ret)
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goto error_out;
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ret = set_memory_x((unsigned long)base, pages);
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if (ret)
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goto error_out;
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mutex_unlock(&part->lock);
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return dst_cpy;
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error_out:
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mutex_unlock(&part->lock);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(sram_exec_copy);
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