Messages in this thread Patch in this message | | | Date | Sat, 20 Jul 2013 17:23:07 +0200 | From | Oleg Nesterov <> | Subject | [PATCH v2 1/1] mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff() |
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mmap() doesn't allow the non-anonymous mappings with VM_GROWS* bit set. In particular this means that mmap_region()->vma_merge(file, vm_flags) must always fail if "vm_flags & VM_GROWS" is set incorrectly.
So it does not make sense to check VM_GROWS* after we already allocated the new vma, the only caller, do_mmap_pgoff(), which can pass this flag can do the check itself.
And this looks a bit more correct, mmap_region() already unmapped the old mapping at this stage. But if mmap() is going to fail, it should avoid do_munmap() if possible.
Note: we check VM_GROWS at the end to ensure that do_mmap_pgoff() won't return EINVAL in the case when it currently returns another error code.
Many thanks to Hugh who nacked the buggy v1.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- mm/mmap.c | 10 ++++------ 1 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c index fbad7b0..92d9f54 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1302,6 +1302,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, if (!file->f_op || !file->f_op->mmap) return -ENODEV; + if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) + return -EINVAL; break; default: @@ -1310,6 +1312,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, } else { switch (flags & MAP_TYPE) { case MAP_SHARED: + if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) + return -EINVAL; /* * Ignore pgoff. */ @@ -1544,11 +1548,7 @@ munmap_back: vma->vm_pgoff = pgoff; INIT_LIST_HEAD(&vma->anon_vma_chain); - error = -EINVAL; /* when rejecting VM_GROWSDOWN|VM_GROWSUP */ - if (file) { - if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) - goto free_vma; if (vm_flags & VM_DENYWRITE) { error = deny_write_access(file); if (error) @@ -1573,8 +1573,6 @@ munmap_back: pgoff = vma->vm_pgoff; vm_flags = vma->vm_flags; } else if (vm_flags & VM_SHARED) { - if (unlikely(vm_flags & (VM_GROWSDOWN|VM_GROWSUP))) - goto free_vma; error = shmem_zero_setup(vma); if (error) goto free_vma; -- 1.5.5.1
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