-stable review patch. If anyone has any objections, please let us know. ------------------ From: Hugh Dickins 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 Signed-off-by: Greg Kroah-Hartman --- mm/madvise.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -159,9 +159,10 @@ static long madvise_remove(struct vm_are 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_are + ((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 lon 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); -- - 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/