diff options
| author | Hugh Dickins <hugh@veritas.com> | 2007-04-13 18:27:55 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-05-01 17:05:56 -0700 |
| commit | 64f586d81ecc913a557055d4804c987f8c766888 (patch) | |
| tree | 9fa41d46aa20c9cbf3d583cd2cdefaf4c90cdaa7 /mm | |
| parent | 42988ea6a81e888a6aa28549071e00400b68f4f7 (diff) | |
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
| -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); |