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btrfs: convert extent_map.refs from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Elena Reshetova
2017-03-03 10:55:12 +02:00
committed by David Sterba
parent 9b64f57ddf
commit 490b54d6fb
6 changed files with 12 additions and 11 deletions
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2
fs/btrfs/tree-log.c
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@@ -4196,7 +4196,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
if (em->generation <= test_gen)
continue;
/* Need a ref to keep it from getting evicted from cache */
atomic_inc(&em->refs);
refcount_inc(&em->refs);
set_bit(EXTENT_FLAG_LOGGING, &em->flags);
list_add_tail(&em->list, &extents);
num++;