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| author | Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> | 2005-09-21 09:55:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-21 10:11:55 -0700 |
| commit | 7e2cff42cfac27c25202648c5c89f9171e5bc085 (patch) | |
| tree | 5579fa13b1fc8081201f05d687e6dc795d9d648f /mm/mprotect.c | |
| parent | 7e871b6c8f1f4fda41e51ef86147facecac3be9f (diff) | |
| download | lwn-7e2cff42cfac27c25202648c5c89f9171e5bc085.tar.gz lwn-7e2cff42cfac27c25202648c5c89f9171e5bc085.zip | |
[PATCH] mm: add a note about partially hardcoded VM_* flags
Hugh made me note this line for permission checking in mprotect():
if ((newflags & ~(newflags >> 4)) & 0xf) {
after figuring out what's that about, I decided it's nasty enough. Btw
Hugh itself didn't like the 0xf.
We can safely change it to VM_READ|VM_WRITE|VM_EXEC because we never change
VM_SHARED, so no need to check that.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index e9fbd013ad9a..57577f63b305 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -248,7 +248,8 @@ sys_mprotect(unsigned long start, size_t len, unsigned long prot) newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); - if ((newflags & ~(newflags >> 4)) & 0xf) { + /* newflags >> 4 shift VM_MAY% in place of VM_% */ + if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { error = -EACCES; goto out; } |