diff options
| author | Hugh Dickins <hugh@veritas.com> | 2007-03-29 01:20:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-29 08:22:26 -0700 |
| commit | 90ed52ebe48181d3c5427b3bd1d24f659e7575ad (patch) | |
| tree | bfb735ab12ebe7964714c637bcb64163646cd347 | |
| parent | 16a100190d39592d1d56ff5a0b978b20288c3427 (diff) | |
[PATCH] holepunch: fix mmap_sem i_mutex deadlock
sys_madvise has down_write of mmap_sem, then madvise_remove calls
vmtruncate_range which takes i_mutex and i_alloc_sem: no, we can easily devise
deadlocks from that ordering.
madvise_remove drop mmap_sem while calling vmtruncate_range: luckily, since
madvise_remove doesn't split or merge vmas, it's easy to handle this case with
a NULL prev, without restructuring sys_madvise. (Though sad to retake
mmap_sem when it's unlikely to be needed, and certainly down_read is
sufficient for MADV_REMOVE, unlike the other madvices.)
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/madvise.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/mm/madvise.c b/mm/madvise.c index 77916e9fc52..603c5257ed6 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -159,9 +159,10 @@ static long madvise_remove(struct vm_area_struct *vma, unsigned long start, unsigned long end) { struct address_space *mapping; - loff_t offset, endoff; + loff_t offset, endoff; + int error; - *prev = vma; + *prev = NULL; /* tell sys_madvise we drop mmap_sem */ if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) return -EINVAL; @@ -180,7 +181,12 @@ static long madvise_remove(struct vm_area_struct *vma, + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); endoff = (loff_t)(end - vma->vm_start - 1) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); - return vmtruncate_range(mapping->host, offset, endoff); + + /* vmtruncate_range needs to take i_mutex and i_alloc_sem */ + up_write(¤t->mm->mmap_sem); + error = vmtruncate_range(mapping->host, offset, endoff); + down_write(¤t->mm->mmap_sem); + return error; } static long @@ -315,12 +321,15 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) if (error) goto out; start = tmp; - if (start < prev->vm_end) + if (prev && start < prev->vm_end) start = prev->vm_end; error = unmapped_error; if (start >= end) goto out; - vma = prev->vm_next; + if (prev) + vma = prev->vm_next; + else /* madvise_remove dropped mmap_sem */ + vma = find_vma(current->mm, start); } out: up_write(¤t->mm->mmap_sem); |