Re: [Qemu-devel] [PATCH] linux-user/syscall: let recvfrom(struct sockaddr *) use abi_ulong

["Guido Günther" <agx@sigxcpu.org>]

Hi,
Thanks for having a look!

On Tue, Jan 23, 2018 at 11:52:22AM -0300, Philippe Mathieu-Daudé wrote:
> Currently recvfrom() is restricted to handle 32-bit pointers,
> remove this limit for 64-bit hosts.
> 
> This fixes:
> 
>   31572 socket(AF_NETLINK, SOCK_RAW, NETLINK_AUDIT) = 3
>   ...
>   31572 sendto(3, {{len=124, type=0x454 /* NLMSG_??? */, flags=NLM_F_REQUEST|NLM_F_ACK, seq=1, pid=0}, "op=test:message acct=\"?\" exe=\"/tmp/nl-bad-addr\" hostname=localhost addr=? terminal=/dev/pts/2 res=success\0\0\0"}, 124, 0, 0xfffffa3897d0, 0) = 124
>   31572 ppoll([{fd=3, events=POLLIN}], 1, {tv_sec=0, tv_nsec=500000000}, NULL, 0) = 1 ([{fd=3, revents=POLLIN}], left {tv_sec=0, tv_nsec=499993180})
>   31572 recvfrom(3, 0x112a50eb4, 8988, MSG_PEEK|MSG_DONTWAIT, 0xfffffa3897e0, 0x42) = -1 EFAULT (Bad address)
> 
> Reported-by: Guido Günther <agx@sigxcpu.org>
> Message-id: 20180123120541.GA14216@bogon.m.sigxcpu.org
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  linux-user/syscall.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 11c9116c4a..28805b1785 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -4032,7 +4032,7 @@ static abi_long do_recvfrom(int fd, abi_ulong msg, size_t len, int flags,
>      if (!host_msg)
>          return -TARGET_EFAULT;
>      if (target_addr) {
> -        if (get_user_u32(addrlen, target_addrlen)) {
> +        if (get_user_ual(addrlen, target_addrlen)) {
>              ret = -TARGET_EFAULT;
>              goto fail;
>          }
> @@ -4053,7 +4053,7 @@ static abi_long do_recvfrom(int fd, abi_ulong msg, size_t len, int flags,
>          }
>          if (target_addr) {
>              host_to_target_sockaddr(target_addr, addr, addrlen);
> -            if (put_user_u32(addrlen, target_addrlen)) {
> +            if (put_user_ual(addrlen, target_addrlen)) {
>                  ret = -TARGET_EFAULT;
>                  goto fail;
>              }

Ahh...I saw these and was wondering how this would work on
64bit. Unfortunately the patch doesn't change things:

    4824  recvfrom(3, 0x1401f8eb4, 8988, MSG_PEEK|MSG_DONTWAIT, 0xffffe10a8620, 0x42) = -1 EFAULT (Bad address)

If you want me to report qemu -strace or s.th. please let me know.
Cheers,
 -- Guido