From: Linus Torvalds Date: Wed, 18 May 2005 22:39:33 +0000 (-0700) Subject: [PATCH] prevent NULL mmap in topdown model X-Git-Tag: v2.6.12-rc5~48 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49a43876b935c811cfd29d8fe998a6912a1cc5c4;p=linux-2.6 [PATCH] prevent NULL mmap in topdown model Prevent the topdown allocator from allocating mmap areas all the way down to address zero. We still allow a MAP_FIXED mapping of page 0 (needed for various things, ranging from Wine and DOSEMU to people who want to allow speculative loads off a NULL pointer). Tested by Chris Wright. Signed-off-by: Linus Torvalds --- diff --git a/mm/mmap.c b/mm/mmap.c index 01f9793591..63df2d6984 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1244,7 +1244,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, addr = mm->free_area_cache; /* make sure it can fit in the remaining address space */ - if (addr >= len) { + if (addr > len) { vma = find_vma(mm, addr-len); if (!vma || addr <= vma->vm_start) /* remember the address as a hint for next time */ @@ -1266,7 +1266,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, /* try just below the current vma->vm_start */ addr = vma->vm_start-len; - } while (len <= vma->vm_start); + } while (len < vma->vm_start); /* * A failed mmap() very likely causes application failure,