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    Subject[PATCH 4.2.y-ckt 051/268] udf: limit the maximum number of indirect extents in a row
    Date
    4.2.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: Vegard Nossum <vegard.nossum@oracle.com>

    commit b0918d9f476a8434b055e362b83fa4fd1d462c3f upstream.

    udf_next_aext() just follows extent pointers while extents are marked as
    indirect. This can loop forever for corrupted filesystem. Limit number
    the of indirect extents we are willing to follow in a row.

    [JK: Updated changelog, limit, style]

    Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
    Cc: Jan Kara <jack@suse.com>
    Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    fs/udf/inode.c | 15 +++++++++++++++
    1 file changed, 15 insertions(+)

    diff --git a/fs/udf/inode.c b/fs/udf/inode.c
    index 8d0b3ad..566df9b 100644
    --- a/fs/udf/inode.c
    +++ b/fs/udf/inode.c
    @@ -2047,14 +2047,29 @@ void udf_write_aext(struct inode *inode, struct extent_position *epos,
    epos->offset += adsize;
    }

    +/*
    + * Only 1 indirect extent in a row really makes sense but allow upto 16 in case
    + * someone does some weird stuff.
    + */
    +#define UDF_MAX_INDIR_EXTS 16
    +
    int8_t udf_next_aext(struct inode *inode, struct extent_position *epos,
    struct kernel_lb_addr *eloc, uint32_t *elen, int inc)
    {
    int8_t etype;
    + unsigned int indirections = 0;

    while ((etype = udf_current_aext(inode, epos, eloc, elen, inc)) ==
    (EXT_NEXT_EXTENT_ALLOCDECS >> 30)) {
    int block;
    +
    + if (++indirections > UDF_MAX_INDIR_EXTS) {
    + udf_err(inode->i_sb,
    + "too many indirect extents in inode %lu\n",
    + inode->i_ino);
    + return -1;
    + }
    +
    epos->block = *eloc;
    epos->offset = sizeof(struct allocExtDesc);
    brelse(epos->bh);
    --
    1.9.1
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