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Only a small subset of mmap(2)'s flags should be used in combination with

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the flag MAP_GUARD.  Rather than enumerating the flags that are not
allowed, enumerate the flags that are allowed.  The list of allowed flags
is much shorter and less likely to change.  (As an aside, one of the
previously enumerated flags, MAP_PREFAULT, was not even a legal flag for
mmap(2).  However, because of an earlier check within kern_mmap(), this
misuse of MAP_PREFAULT was harmless.)

Reviewed by:	kib
MFC after:	10 days
This commit is contained in:
Alan Cox 2018-06-01 21:37:42 +00:00
parent 3254c39f83
commit 60221a5701
1 changed files with 2 additions and 2 deletions
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4
sys/vm/vm_mmap.c
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@ -241,8 +241,8 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t size, int prot, int flags,
(prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)) != 0)
return (EINVAL);
if ((flags & MAP_GUARD) != 0 && (prot != PROT_NONE || fd != -1 ||
pos != 0 || (flags & (MAP_SHARED | MAP_PRIVATE | MAP_PREFAULT |
MAP_PREFAULT_READ | MAP_ANON | MAP_STACK)) != 0))
pos != 0 || (flags & ~(MAP_FIXED | MAP_GUARD | MAP_EXCL |
MAP_32BIT | MAP_ALIGNMENT_MASK)) != 0))
return (EINVAL);
/*