Hi David,
On Thu, Nov 14, 2024 at 9:30 PM David Wei <dw@xxxxxxxxxxx> wrote:
>
> On 2024-11-14 18:15, Luiz Augusto von Dentz wrote:
> > Hi David,
> >
> > On Thu, Nov 14, 2024 at 7:42 PM David Wei <dw@xxxxxxxxxxx> wrote:
> >>
> >> On 2024-11-14 15:27, Michal Luczaj wrote:
> >>> The bt_copy_from_sockptr() return value is being misinterpreted by most
> >>> users: a non-zero result is mistakenly assumed to represent an error code,
> >>> but actually indicates the number of bytes that could not be copied.
> >>>
> >>> Remove bt_copy_from_sockptr() and adapt callers to use
> >>> copy_safe_from_sockptr().
> >>>
> >>> For sco_sock_setsockopt() (case BT_CODEC) use copy_struct_from_sockptr() to
> >>> scrub parts of uninitialized buffer.
> >>>
> >>> Opportunistically, rename `len` to `optlen` in hci_sock_setsockopt_old()
> >>> and hci_sock_setsockopt().
> >>>
> >>> Fixes: 51eda36d33e4 ("Bluetooth: SCO: Fix not validating setsockopt user input")
> >>> Fixes: a97de7bff13b ("Bluetooth: RFCOMM: Fix not validating setsockopt user input")
> >>> Fixes: 4f3951242ace ("Bluetooth: L2CAP: Fix not validating setsockopt user input")
> >>> Fixes: 9e8742cdfc4b ("Bluetooth: ISO: Fix not validating setsockopt user input")
> >>> Fixes: b2186061d604 ("Bluetooth: hci_sock: Fix not validating setsockopt user input")
> >>> Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
> >>> ---
> >>> include/net/bluetooth/bluetooth.h | 9 ---------
> >>> net/bluetooth/hci_sock.c | 14 +++++++-------
> >>> net/bluetooth/iso.c | 10 +++++-----
> >>> net/bluetooth/l2cap_sock.c | 20 +++++++++++---------
> >>> net/bluetooth/rfcomm/sock.c | 9 ++++-----
> >>> net/bluetooth/sco.c | 11 ++++++-----
> >>> 6 files changed, 33 insertions(+), 40 deletions(-)
> >>>
> >> ...
> >>> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> >>> index f48250e3f2e103c75d5937e1608e43c123aa3297..1001fb4cc21c0ecc7bcdd3ea9041770ede4f27b8 100644
> >>> --- a/net/bluetooth/rfcomm/sock.c
> >>> +++ b/net/bluetooth/rfcomm/sock.c
> >>> @@ -629,10 +629,9 @@ static int rfcomm_sock_setsockopt_old(struct socket *sock, int optname,
> >>>
> >>> switch (optname) {
> >>> case RFCOMM_LM:
> >>> - if (bt_copy_from_sockptr(&opt, sizeof(opt), optval, optlen)) {
> >>> - err = -EFAULT;
> >>> + err = copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen);
> >>> + if (err)
> >>> break;
> >>> - }
> >>
> >> This will return a positive integer if copy_safe_from_sockptr() fails.
> >
> > What are you talking about copy_safe_from_sockptr never returns a
> > positive value:
> >
> > * Returns:
> > * * -EINVAL: @optlen < @ksize
> > * * -EFAULT: access to userspace failed.
> > * * 0 : @ksize bytes were copied
>
> Isn't this what this series is about? copy_from_sockptr() returns 0 on
> success, or a positive integer for number of bytes NOT copied on error.
> Patch 4 even updates the docs for copy_from_sockptr().
>
> copy_safe_from_sockptr()
> -> copy_from_sockptr()
> -> copy_from_sockptr_offset()
> -> memcpy() for kernel to kernel OR
> -> copy_from_user() otherwise
Well except the safe version does check what would otherwise cause a
positive return by the likes of copy_from_user and returns -EINVAL
instead, otherwise the documentation of copy_safe_from_sockptr is just
wrong and shall state that it could return positive as well but I
guess that would just make it as inconvenient so we might as well
detect when a positive value would be returned just return -EFAULT
instead.
> And copy_from_user() follows the same 0 for success or N > 0 for
> failure. It does not EFAULT on its own AFAIK.
>
> The docs for copy_safe_from_sockptr() that you've linked contains the
> exact misunderstanding that Michal is correcting.
>
> >
> >> Shouldn't this be:
> >>
> >> err = -EFAULT;
> >> if (copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen))
> >> break;
> >
> >
> >
--
Luiz Augusto von Dentz
