Messages in this thread Patch in this message | | | Date | Mon, 21 Apr 2003 13:04:27 +0200 | From | DervishD <> | Subject | [RESEND][PATCH] against mmap.c (do_mmap_pgoff) and a note |
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Hi Linus :)
I've noticed that in file 'mm/mmap.c', at the comments for function 'can_vma_merge_before' this can be read:
<quote> * We don't check here for the merged mmap wrapping around the end of pagecache * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which * wrap, nor mmaps which cover the final page at index -1UL. */ </quote>
Well, the patch I sent you against 2.5.60 and that I'm resending, since it's not included at 2.5.68, fixed a mmap() corner case bug, that made mmap() fail for large sizes (as did a previous patch that you did apply) and that works even if 'TASK_SIZE' is the entire address space (as seems the case at sparc64, for example). The problem is that with the patch you already applied and with the new patch I send, you cannot do a mmap that wraps, but you can mmap the final page (not at index -1UL, there is not such index!, -1 unsigned?). In fact, you can mmap your entire address space if you want.
Without the patch you already applied any such 'big' mmap will silently fail, and with the new, if the arch doesn't want such a big mmap it will return EINVAL.
I think the problem in 'can_vma_merge_before' is just the comment (for me it sounds ambiguous), but the other problem, with archs like sparc64, still is an issue. Dave Miller pointed this although I made the patch. Please apply, the semantics of 'do_mmap_pgoff' doesn't change a bit, is just that the current code will silently fail for sparc64 and other archs where TASK_SIZE is the entire address space.
Thanks a lot and happy coding :)
Raúl Núñez de Arenas Coronado
-- Linux Registered User 88736 http://www.pleyades.net & http://raul.pleyades.net/ --- linux/mm/mmap.c.orig 2002-12-11 14:27:04.000000000 +0100 +++ linux/mm/mmap.c 2002-12-11 14:28:09.000000000 +0100 @@ -421,14 +421,14 @@ if (file && (!file->f_op || !file->f_op->mmap)) return -ENODEV; - if (!len) + if (len == 0) return addr; - if (len > TASK_SIZE) - return -EINVAL; - len = PAGE_ALIGN(len); + if (len > TASK_SIZE || len == 0) + return -EINVAL; + /* offset overflow? */ if ((pgoff + (len >> PAGE_SHIFT)) < pgoff) return -EINVAL; | |