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    Subject[PATCH 3.16.y-ckt 098/129] nilfs2: fix sanity check of btree level in nilfs_btree_root_broken()
    Date
    3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

    commit d8fd150fe3935e1692bf57c66691e17409ebb9c1 upstream.

    The range check for b-tree level parameter in nilfs_btree_root_broken()
    is wrong; it accepts the case of "level == NILFS_BTREE_LEVEL_MAX" even
    though the level is limited to values in the range of 0 to
    (NILFS_BTREE_LEVEL_MAX - 1).

    Since the level parameter is read from storage device and used to index
    nilfs_btree_path array whose element count is NILFS_BTREE_LEVEL_MAX, it
    can cause memory overrun during btree operations if the boundary value
    is set to the level parameter on device.

    This fixes the broken sanity check and adds a comment to clarify that
    the upper bound NILFS_BTREE_LEVEL_MAX is exclusive.

    Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    fs/nilfs2/btree.c | 2 +-
    include/linux/nilfs2_fs.h | 2 +-
    2 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
    index ecdbae19a766..090d8ce25bd1 100644
    --- a/fs/nilfs2/btree.c
    +++ b/fs/nilfs2/btree.c
    @@ -388,7 +388,7 @@ static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
    nchildren = nilfs_btree_node_get_nchildren(node);

    if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
    - level > NILFS_BTREE_LEVEL_MAX ||
    + level >= NILFS_BTREE_LEVEL_MAX ||
    nchildren < 0 ||
    nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
    pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, flags = 0x%x, nchildren = %d\n",
    diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
    index ff3fea3194c6..9abb763e4b86 100644
    --- a/include/linux/nilfs2_fs.h
    +++ b/include/linux/nilfs2_fs.h
    @@ -460,7 +460,7 @@ struct nilfs_btree_node {
    /* level */
    #define NILFS_BTREE_LEVEL_DATA 0
    #define NILFS_BTREE_LEVEL_NODE_MIN (NILFS_BTREE_LEVEL_DATA + 1)
    -#define NILFS_BTREE_LEVEL_MAX 14
    +#define NILFS_BTREE_LEVEL_MAX 14 /* Max level (exclusive) */

    /**
    * struct nilfs_palloc_group_desc - block group descriptor

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