[axboe-block:for-6.15/io_uring 55/56] io_uring/net.c:719:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true

[axboe-block:for-6.15/io_uring 55/56] io_uring/net.c:719:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-6.15/io_uring
head:   7eb5bb749ed945ead6a089e18e1d1da74523ac9a
commit: 68525267875757520752ff1abbda0af58fc172b9 [55/56] io_uring/net: unify *mshot_prep calls with compat
config: um-randconfig-001-20250227 (https://download.01.org/0day-ci/archive/20250227/202502270853.xYltEB97-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250227/202502270853.xYltEB97-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502270853.xYltEB97-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> io_uring/net.c:719:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
     719 |         if (io_is_compat(req->ctx)) {
         |             ^~~~~~~~~~~~~~~~~~~~~~
   io_uring/net.c:733:15: note: uninitialized use occurs here
     733 |         if (unlikely(ret))
         |                      ^~~
   include/linux/compiler.h:77:42: note: expanded from macro 'unlikely'
      77 | # define unlikely(x)    __builtin_expect(!!(x), 0)
         |                                             ^
   io_uring/net.c:719:2: note: remove the 'if' if its condition is always false
     719 |         if (io_is_compat(req->ctx)) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     720 | #ifdef CONFIG_COMPAT
         | ~~~~~~~~~~~~~~~~~~~~
     721 |                 struct compat_msghdr cmsg;
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~
     722 | 
     723 |                 ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_DEST,
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     724 |                                              &iomsg->uaddr);
         |                                              ~~~~~~~~~~~~~~~
     725 |                 memset(&msg, 0, sizeof(msg));
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     726 |                 msg.msg_namelen = cmsg.msg_namelen;
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     727 |                 msg.msg_controllen = cmsg.msg_controllen;
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     728 | #endif
         | ~~~~~~
     729 |         } else {
         |         ~~~~~~
   io_uring/net.c:714:9: note: initialize the variable 'ret' to silence this warning
     714 |         int ret;
         |                ^
         |                 = 0
   1 warning generated.


vim +719 io_uring/net.c

c55978024d123d Jens Axboe     2024-02-27  709  
f9ead18c10589a Jens Axboe     2022-05-25  710  static int io_recvmsg_copy_hdr(struct io_kiocb *req,
f9ead18c10589a Jens Axboe     2022-05-25  711  			       struct io_async_msghdr *iomsg)
f9ead18c10589a Jens Axboe     2022-05-25  712  {
7fa875b8e53c28 Dylan Yudaken  2022-07-14  713  	struct user_msghdr msg;
f9ead18c10589a Jens Axboe     2022-05-25  714  	int ret;
f9ead18c10589a Jens Axboe     2022-05-25  715  
c55978024d123d Jens Axboe     2024-02-27  716  	iomsg->msg.msg_name = &iomsg->addr;
c55978024d123d Jens Axboe     2024-02-27  717  	iomsg->msg.msg_iter.nr_segs = 0;
f9ead18c10589a Jens Axboe     2022-05-25  718  
91864064622b17 Pavel Begunkov 2025-02-24 @719  	if (io_is_compat(req->ctx)) {
68525267875757 Pavel Begunkov 2025-02-26  720  #ifdef CONFIG_COMPAT
c55978024d123d Jens Axboe     2024-02-27  721  		struct compat_msghdr cmsg;
72c531f8ef3052 Dylan Yudaken  2022-07-14  722  
820c215726a57f Pavel Begunkov 2025-02-26  723  		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_DEST,
820c215726a57f Pavel Begunkov 2025-02-26  724  					     &iomsg->uaddr);
68525267875757 Pavel Begunkov 2025-02-26  725  		memset(&msg, 0, sizeof(msg));
68525267875757 Pavel Begunkov 2025-02-26  726  		msg.msg_namelen = cmsg.msg_namelen;
68525267875757 Pavel Begunkov 2025-02-26  727  		msg.msg_controllen = cmsg.msg_controllen;
f9ead18c10589a Jens Axboe     2022-05-25  728  #endif
68525267875757 Pavel Begunkov 2025-02-26  729  	} else {
820c215726a57f Pavel Begunkov 2025-02-26  730  		ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_DEST, &iomsg->uaddr);
68525267875757 Pavel Begunkov 2025-02-26  731  	}
68525267875757 Pavel Begunkov 2025-02-26  732  
c55978024d123d Jens Axboe     2024-02-27  733  	if (unlikely(ret))
c55978024d123d Jens Axboe     2024-02-27  734  		return ret;
c55978024d123d Jens Axboe     2024-02-27  735  	return io_recvmsg_mshot_prep(req, iomsg, msg.msg_namelen,
c55978024d123d Jens Axboe     2024-02-27  736  					msg.msg_controllen);
f9ead18c10589a Jens Axboe     2022-05-25  737  }
f9ead18c10589a Jens Axboe     2022-05-25  738  

:::::: The code at line 719 was first introduced by commit
:::::: 91864064622b17e74f49fd42689a052eaac4f08e io_uring/net: use io_is_compat()

:::::: TO: Pavel Begunkov <asml.silence@gmail.com>
:::::: CC: Jens Axboe <axboe@kernel.dk>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [axboe-block:for-6.15/io_uring 55/56] io_uring/net.c:719:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true

[Pavel Begunkov]

On 2/27/25 00:12, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-6.15/io_uring
> head:   7eb5bb749ed945ead6a089e18e1d1da74523ac9a
> commit: 68525267875757520752ff1abbda0af58fc172b9 [55/56] io_uring/net: unify *mshot_prep calls with compat
> config: um-randconfig-001-20250227 (https://download.01.org/0day-ci/archive/20250227/202502270853.xYltEB97-lkp@intel.com/config)
> compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250227/202502270853.xYltEB97-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202502270853.xYltEB97-lkp@intel.com/

Not a real problem, it's just the compiler (understandably) can't
derive that the block is only empty IFF io_is_compat() is a
constant false.

We can initialise the var and let the compiler optimise it to
silence the warning.

-- 
Pavel Begunkov