Messages in this thread Patch in this message | | | From | Paolo 'Blaisorblade' Giarrusso <> | Subject | [PATCH 7/7] Add a note about partially hardcoded VM_* flags | Date | Tue, 20 Sep 2005 20:46:03 +0200 |
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
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.
CC: Hugh Dickins <hugh@veritas.com> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> ---
include/linux/mm.h | 1 + mm/mprotect.c | 3 ++- 2 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -136,6 +136,7 @@ extern unsigned int kobjsize(const void #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 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -248,7 +248,8 @@ sys_mprotect(unsigned long start, size_t 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; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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