Revision a57b70519d1f7c53be98478623652738e5ac70d5 authored by Liam Howlett on 18 October 2022, 19:17:12 UTC, committed by Andrew Morton on 21 October 2022, 04:27:23 UTC
mmap should return the start address of newly mapped area when successful. On a successful merge of a VMA, the return address was changed and thus was violating that expectation from userspace. This is a restoration of functionality provided by 309d08d9b3a3 (mm/mmap.c: fix mmap return value when vma is merged after call_mmap()). For completeness of fixing MAP_FIXED, implement the comments from the previous discussion to never update the address and fail if the address changes. Leaving the error as a WARN_ON() to avoid crashing the kernel. Link: https://lkml.kernel.org/r/20221018191613.4133459-1-Liam.Howlett@oracle.com Link: https://lore.kernel.org/all/Y06yk66SKxlrwwfb@lakrids/ Link: https://lore.kernel.org/all/20201203085350.22624-1-liuzixian4@huawei.com/ Fixes: 4dd1b84140c1 ("mm/mmap: use advanced maple tree API for mmap_region()") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reported-by: Mark Rutland <mark.rutland@arm.com> Cc: Liu Zixian <liuzixian4@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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encoding.h
/* SPDX-License-Identifier: GPL-2.0 */
/*
* KCSAN watchpoint encoding.
*
* Copyright (C) 2019, Google LLC.
*/
#ifndef _KERNEL_KCSAN_ENCODING_H
#define _KERNEL_KCSAN_ENCODING_H
#include <linux/bits.h>
#include <linux/log2.h>
#include <linux/mm.h>
#include "kcsan.h"
#define SLOT_RANGE PAGE_SIZE
#define INVALID_WATCHPOINT 0
#define CONSUMED_WATCHPOINT 1
/*
* The maximum useful size of accesses for which we set up watchpoints is the
* max range of slots we check on an access.
*/
#define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT))
/*
* Number of bits we use to store size info.
*/
#define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE)
/*
* This encoding for addresses discards the upper (1 for is-write + SIZE_BITS);
* however, most 64-bit architectures do not use the full 64-bit address space.
* Also, in order for a false positive to be observable 2 things need to happen:
*
* 1. different addresses but with the same encoded address race;
* 2. and both map onto the same watchpoint slots;
*
* Both these are assumed to be very unlikely. However, in case it still
* happens, the report logic will filter out the false positive (see report.c).
*/
#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)
/* Bitmasks for the encoded watchpoint access information. */
#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
#define WATCHPOINT_SIZE_MASK GENMASK(BITS_PER_LONG-2, WATCHPOINT_ADDR_BITS)
#define WATCHPOINT_ADDR_MASK GENMASK(WATCHPOINT_ADDR_BITS-1, 0)
static_assert(WATCHPOINT_ADDR_MASK == (1UL << WATCHPOINT_ADDR_BITS) - 1);
static_assert((WATCHPOINT_WRITE_MASK ^ WATCHPOINT_SIZE_MASK ^ WATCHPOINT_ADDR_MASK) == ~0UL);
static inline bool check_encodable(unsigned long addr, size_t size)
{
/*
* While we can encode addrs<PAGE_SIZE, avoid crashing with a NULL
* pointer deref inside KCSAN.
*/
return addr >= PAGE_SIZE && size <= MAX_ENCODABLE_SIZE;
}
static inline long
encode_watchpoint(unsigned long addr, size_t size, bool is_write)
{
return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
(size << WATCHPOINT_ADDR_BITS) |
(addr & WATCHPOINT_ADDR_MASK));
}
static __always_inline bool decode_watchpoint(long watchpoint,
unsigned long *addr_masked,
size_t *size,
bool *is_write)
{
if (watchpoint == INVALID_WATCHPOINT ||
watchpoint == CONSUMED_WATCHPOINT)
return false;
*addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
*size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >> WATCHPOINT_ADDR_BITS;
*is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
return true;
}
/*
* Return watchpoint slot for an address.
*/
static __always_inline int watchpoint_slot(unsigned long addr)
{
return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS;
}
static __always_inline bool matching_access(unsigned long addr1, size_t size1,
unsigned long addr2, size_t size2)
{
unsigned long end_range1 = addr1 + size1 - 1;
unsigned long end_range2 = addr2 + size2 - 1;
return addr1 <= end_range2 && addr2 <= end_range1;
}
#endif /* _KERNEL_KCSAN_ENCODING_H */
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