1869305009
The vm_populate() code populates user mappings without constantly holding the mmap_sem. This makes it susceptible to racy userspace programs: the user mappings may change while vm_populate() is running, and in this case vm_populate() may end up populating the new mapping instead of the old one. In order to reduce the possibility of userspace getting surprised by this behavior, this change introduces the VM_POPULATE vma flag which gets set on vmas we want vm_populate() to work on. This way vm_populate() may still end up populating the new mapping after such a race, but only if the new mapping is also one that the user has requested (using MAP_SHARED, MAP_LOCKED or mlock) to be populated. Signed-off-by: Michel Lespinasse <walken@google.com> Acked-by: Rik van Riel <riel@redhat.com> Tested-by: Andy Lutomirski <luto@amacapital.net> Cc: Greg Ungerer <gregungerer@westnet.com.au> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
86 lines
2.1 KiB
C
86 lines
2.1 KiB
C
#ifndef _LINUX_MMAN_H
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#define _LINUX_MMAN_H
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#include <linux/mm.h>
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#include <linux/percpu_counter.h>
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#include <linux/atomic.h>
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#include <uapi/linux/mman.h>
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extern int sysctl_overcommit_memory;
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extern int sysctl_overcommit_ratio;
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extern struct percpu_counter vm_committed_as;
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unsigned long vm_memory_committed(void);
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static inline void vm_acct_memory(long pages)
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{
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percpu_counter_add(&vm_committed_as, pages);
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}
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static inline void vm_unacct_memory(long pages)
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{
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vm_acct_memory(-pages);
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}
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/*
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* Allow architectures to handle additional protection bits
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*/
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#ifndef arch_calc_vm_prot_bits
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#define arch_calc_vm_prot_bits(prot) 0
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#endif
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#ifndef arch_vm_get_page_prot
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#define arch_vm_get_page_prot(vm_flags) __pgprot(0)
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#endif
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#ifndef arch_validate_prot
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/*
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* This is called from mprotect(). PROT_GROWSDOWN and PROT_GROWSUP have
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* already been masked out.
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*
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* Returns true if the prot flags are valid
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*/
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static inline int arch_validate_prot(unsigned long prot)
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{
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return (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) == 0;
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}
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#define arch_validate_prot arch_validate_prot
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#endif
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/*
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* Optimisation macro. It is equivalent to:
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* (x & bit1) ? bit2 : 0
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* but this version is faster.
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* ("bit1" and "bit2" must be single bits)
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*/
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#define _calc_vm_trans(x, bit1, bit2) \
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((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \
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: ((x) & (bit1)) / ((bit1) / (bit2)))
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/*
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* Combine the mmap "prot" argument into "vm_flags" used internally.
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*/
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static inline unsigned long
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calc_vm_prot_bits(unsigned long prot)
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{
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return _calc_vm_trans(prot, PROT_READ, VM_READ ) |
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_calc_vm_trans(prot, PROT_WRITE, VM_WRITE) |
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_calc_vm_trans(prot, PROT_EXEC, VM_EXEC) |
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arch_calc_vm_prot_bits(prot);
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}
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/*
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* Combine the mmap "flags" argument into "vm_flags" used internally.
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*/
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static inline unsigned long
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calc_vm_flag_bits(unsigned long flags)
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{
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return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
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_calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) |
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((flags & MAP_LOCKED) ? (VM_LOCKED | VM_POPULATE) : 0) |
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(((flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE) ?
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VM_POPULATE : 0);
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}
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#endif /* _LINUX_MMAN_H */
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