fs/nilfs2: fix integer overflow in nilfs_ioctl_wrap_copy()
The local variable 'pos' in nilfs_ioctl_wrap_copy function can overflow if a large number was passed to argv->v_index from userspace and the sum of argv->v_index and argv->v_nmembs exceeds the maximum value of __u64 type integer (= ~(__u64)0 = 18446744073709551615). Here, argv->v_index is a 64-bit width argument to specify the start position of target data items (such as segment number, checkpoint number, or virtual block address of nilfs), and argv->v_nmembs gives the total number of the items that userland programs (such as lssu, lscp, or cleanerd) want to get information about, which also gives the maximum element count of argv->v_base[] array. nilfs_ioctl_wrap_copy() calls dofunc() repeatedly and increments the position variable 'pos' at the end of each iteration if dofunc() itself didn't update 'pos': if (pos == ppos) pos += n; This patch prevents the overflow here by rejecting pairs of a start position (argv->v_index) and a total count (argv->v_nmembs) which leads to the overflow. [konishi.ryusuke@lab.ntt.co.jp: fix signedness issue] Signed-off-by: Wenliang Fan <fanwlexca@gmail.com> Cc: Vyacheslav Dubeyko <slava@dubeyko.com> 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>
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