Re: [PATCH] RDMA/core: Check for the presence of LS_NLA_TYPE_DGID correctly

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Nov 28, 2025 at 01:37:28PM -0400, Jason Gunthorpe wrote:
> The netlink response for RDMA_NL_LS_OP_IP_RESOLVE should always have a
> LS_NLA_TYPE_DGID attribute, it is invalid if it does not.
> 
> Use the nl parsing logic properly and call nla_parse_deprecated() to fill
> the nlattrs array and then directly index that array to get the data for
> the DGID. Just fail if it is NULL.
> 
> Remove the for loop searching for the nla, and squash the validation and
> parsing into one function.
> 
> Fixes an uninitialized read from the stack triggered by userspace if it
> does not provide the DGID to a kernel initiated RDMA_NL_LS_OP_IP_RESOLVE
> query.
> 
>     BUG: KMSAN: uninit-value in hex_byte_pack include/linux/hex.h:13 [inline]
>     BUG: KMSAN: uninit-value in ip6_string+0xef4/0x13a0 lib/vsprintf.c:1490
>      hex_byte_pack include/linux/hex.h:13 [inline]
>      ip6_string+0xef4/0x13a0 lib/vsprintf.c:1490
>      ip6_addr_string+0x18a/0x3e0 lib/vsprintf.c:1509
>      ip_addr_string+0x245/0xee0 lib/vsprintf.c:1633
>      pointer+0xc09/0x1bd0 lib/vsprintf.c:2542
>      vsnprintf+0xf8a/0x1bd0 lib/vsprintf.c:2930
>      vprintk_store+0x3ae/0x1530 kernel/printk/printk.c:2279
>      vprintk_emit+0x307/0xcd0 kernel/printk/printk.c:2426
>      vprintk_default+0x3f/0x50 kernel/printk/printk.c:2465
>      vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
>      _printk+0x17e/0x1b0 kernel/printk/printk.c:2475
>      ib_nl_process_good_ip_rsep drivers/infiniband/core/addr.c:128 [inline]
>      ib_nl_handle_ip_res_resp+0x963/0x9d0 drivers/infiniband/core/addr.c:141
>      rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:-1 [inline]
>      rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
>      rdma_nl_rcv+0xefa/0x11c0 drivers/infiniband/core/netlink.c:259
>      netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
>      netlink_unicast+0xf04/0x12b0 net/netlink/af_netlink.c:1346
>      netlink_sendmsg+0x10b3/0x1250 net/netlink/af_netlink.c:1896
>      sock_sendmsg_nosec net/socket.c:714 [inline]
>      __sock_sendmsg+0x333/0x3d0 net/socket.c:729
>      ____sys_sendmsg+0x7e0/0xd80 net/socket.c:2617
>      ___sys_sendmsg+0x271/0x3b0 net/socket.c:2671
>      __sys_sendmsg+0x1aa/0x300 net/socket.c:2703
>      __compat_sys_sendmsg net/compat.c:346 [inline]
>      __do_compat_sys_sendmsg net/compat.c:353 [inline]
>      __se_compat_sys_sendmsg net/compat.c:350 [inline]
>      __ia32_compat_sys_sendmsg+0xa4/0x100 net/compat.c:350
>      ia32_sys_call+0x3f6c/0x4310 arch/x86/include/generated/asm/syscalls_32.h:371
>      do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
>      __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
>      do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
>      do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:3
> 
> Cc: stable@vger.kernel.org
> Fixes: ae43f8286730 ("IB/core: Add IP to GID netlink offload")
> Reported-by: syzbot+938fcd548c303fe33c1a@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/r/68dc3dac.a00a0220.102ee.004f.GAE@google.com
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/infiniband/core/addr.c | 33 ++++++++++-----------------------
>  1 file changed, 10 insertions(+), 23 deletions(-)

Applied to for-rc

Jason