genhd: check for int overflow in disk_expand_part_tbl()
commit 5fabcb4c upstream. We can get here from blkdev_ioctl() -> blkpg_ioctl() -> add_partition() with a user passed in partno value. If we pass in 0x7fffffff, the new target in disk_expand_part_tbl() overflows the 'int' and we access beyond the end of ptbl->part[] and even write to it when we do the rcu_assign_pointer() to assign the new partition. Reported-by: David Ramos <daramos@stanford.edu> Signed-off-by: Jens Axboe <axboe@fb.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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