iommufd: Prevent ALIGN() overflow

When allocating IOVA the candidate range gets aligned to the target
alignment. If the range is close to ULONG_MAX then the ALIGN() can
wrap resulting in a corrupted iova.

Open code the ALIGN() using get_add_overflow() to prevent this.
This simplifies the checks as we don't need to check for length earlier
either.

Consolidate the two copies of this code under a single helper.

This bug would allow userspace to create a mapping that overlaps with some
other mapping or a reserved range.

Cc: [email protected]
Fixes: 51fe6141f0f6 ("iommufd: Data structure to provide IOVA to PFN mapping")
Reported-by: [email protected]
Closes: https://lore.kernel.org/r/[email protected]
Reviewed-by: Yi Liu <[email protected]>
Reviewed-by: Nicolin Chen <[email protected]>
Link: https://patch.msgid.link/all/[email protected]/
Signed-off-by: Jason Gunthorpe <[email protected]>

0 files changed, 0 insertions, 0 deletions