We check if ->ki_pos is positive. However, by that point we have
already done rw_verify_area(), which would have rejected such
unless the file had been one of /dev/mem, /dev/kmem and /proc/kcore.
All of which do not have vectored rw methods, so we would've bailed
out even earlier.
This check had been introduced before rw_verify_area() had been added there
- in fact, it was a subset of checks done on sync paths by rw_verify_area()
(back then the /dev/mem exception didn't exist at all). The rest of checks
(mandatory locking, etc.) hadn't been added until later. Unfortunately,
by the time the call of rw_verify_area() got added, the /dev/mem exception
had already appeared, so it wasn't obvious that the older explicit check
downstream had become dead code. It *is* a dead code, though, since the few
files for which the exception applies do not have ->aio_{read,write}() or
->{read,write}_iter() and for them we won't reach that check anyway.
What's more, even if we ever introduce vectored methods for /dev/mem
and friends, they'll have to cope with negative positions anyway, since
readv(2) and writev(2) are using the same checks as read(2) and write(2) -
i.e. rw_verify_area().
Let's bury it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Way, way back kiocb used to be picked from arrays, so ioctx_alloc()
checked for multiplication overflow when calculating the size of
such array. By the time fs/aio.c went into the tree (in 2002) they
were already allocated one-by-one by kmem_cache_alloc(), so that
check had already become pointless. Let's bury it...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
unfortunately, allowing an arbitrary 16bit value means a possibility of
overflow in the calculation of total number of pages in bio_map_user_iov() -
we rely on there being no more than PAGE_SIZE members of sum in the
first loop there. If that sum wraps around, we end up allocating
too small array of pointers to pages and it's easy to overflow it in
the second loop.
X-Coverup: TINC (and there's no lumber cartel either)
Cc: stable@vger.kernel.org # way, way back
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Al Viro