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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 | |
| parent | [PATCH] mm: update stale comment for removal of page->list (diff) | |
| download | linux-dev-7e2cff42cfac27c25202648c5c89f9171e5bc085.tar.xz linux-dev-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>
| -rw-r--r-- | include/linux/mm.h | 1 | ||||
| -rw-r--r-- | mm/mprotect.c | 3 |
2 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 0d94c94d9d81..097b3a3c693d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -136,6 +136,7 @@ extern unsigned int kobjsize(const void *objp); #define VM_EXEC 0x00000004 #define VM_SHARED 0x00000008 +/* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */ #define VM_MAYREAD 0x00000010 /* limits for mprotect() etc */ #define VM_MAYWRITE 0x00000020 #define VM_MAYEXEC 0x00000040 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; } |