Re: [PATCH v2 2/2] NFSv4 account for selinux security context when deciding to share superblock

[Dan Carpenter <dan.carpenter@oracle.com>]

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Hi Olga,

url:    https://github.com/0day-ci/linux/commits/Olga-Kornievskaia/Add-new-hook-to-compare-new-mount-to-an-existing-mount/20210219-035957
base:   git://git.linux-nfs.org/projects/trondmy/linux-nfs.git linux-next
config: i386-randconfig-m021-20210215 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
fs/nfs/super.c:1061 nfs_fill_super() error: we previously assumed 'ctx' could be null (see line 1029)

vim +/ctx +1061 fs/nfs/super.c

62a55d088cd87d Scott Mayhew      2019-12-10  1021  static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
f7b422b17ee5ee David Howells     2006-06-09  1022  {
54ceac45159860 David Howells     2006-08-22  1023  	struct nfs_server *server = NFS_SB(sb);
f7b422b17ee5ee David Howells     2006-06-09  1024  
f7b422b17ee5ee David Howells     2006-06-09  1025  	sb->s_blocksize_bits = 0;
f7b422b17ee5ee David Howells     2006-06-09  1026  	sb->s_blocksize = 0;
6a74490dca8974 Bryan Schumaker   2012-07-30  1027  	sb->s_xattr = server->nfs_client->cl_nfs_mod->xattr;
6a74490dca8974 Bryan Schumaker   2012-07-30  1028  	sb->s_op = server->nfs_client->cl_nfs_mod->sops;
5eb005caf5383d David Howells     2019-12-10 @1029  	if (ctx && ctx->bsize)
                                                            ^^^
Check for NULL

5eb005caf5383d David Howells     2019-12-10  1030  		sb->s_blocksize = nfs_block_size(ctx->bsize, &sb->s_blocksize_bits);
f7b422b17ee5ee David Howells     2006-06-09  1031  
6a74490dca8974 Bryan Schumaker   2012-07-30  1032  	if (server->nfs_client->rpc_ops->version != 2) {
54ceac45159860 David Howells     2006-08-22  1033  		/* The VFS shouldn't apply the umask to mode bits. We will do
54ceac45159860 David Howells     2006-08-22  1034  		 * so ourselves when necessary.
54ceac45159860 David Howells     2006-08-22  1035  		 */
1751e8a6cb935e Linus Torvalds    2017-11-27  1036  		sb->s_flags |= SB_POSIXACL;
54ceac45159860 David Howells     2006-08-22  1037  		sb->s_time_gran = 1;
20fa1902728698 Peng Tao          2017-06-29  1038  		sb->s_export_op = &nfs_export_ops;
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1039  	} else
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1040  		sb->s_time_gran = 1000;
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1041  
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1042  	if (server->nfs_client->rpc_ops->version != 4) {
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1043  		sb->s_time_min = 0;
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1044  		sb->s_time_max = U32_MAX;
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1045  	} else {
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1046  		sb->s_time_min = S64_MIN;
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1047  		sb->s_time_max = S64_MAX;
54ceac45159860 David Howells     2006-08-22  1048  	}
f7b422b17ee5ee David Howells     2006-06-09  1049  
ab88dca311a372 Al Viro           2019-12-10  1050  	sb->s_magic = NFS_SUPER_MAGIC;
54ceac45159860 David Howells     2006-08-22  1051  
ab88dca311a372 Al Viro           2019-12-10  1052  	/* We probably want something more informative here */
ab88dca311a372 Al Viro           2019-12-10  1053  	snprintf(sb->s_id, sizeof(sb->s_id),
ab88dca311a372 Al Viro           2019-12-10  1054  		 "%u:%u", MAJOR(sb->s_dev), MINOR(sb->s_dev));
1fcb79c1b21801 Deepa Dinamani    2019-03-26  1055  
ab88dca311a372 Al Viro           2019-12-10  1056  	if (sb->s_blocksize == 0)
ab88dca311a372 Al Viro           2019-12-10  1057  		sb->s_blocksize = nfs_block_bits(server->wsize,
ab88dca311a372 Al Viro           2019-12-10  1058  						 &sb->s_blocksize_bits);
f7b422b17ee5ee David Howells     2006-06-09  1059  
ab88dca311a372 Al Viro           2019-12-10  1060  	nfs_super_set_maxbytes(sb, server->maxfilesize);
52a2a3a4af9af7 Olga Kornievskaia 2021-02-18 @1061  	server->has_sec_mnt_opts = ctx->has_sec_mnt_opts;
                                                                                   ^^^^^^^^^^^^^^^^^^^^^
Unchecked dereference.  Is the earlier NULL check necessary?  (Actually
on my system with a built cross function DB, I see that the earlier
NULL check can be removed.  If the cross function DB were built then
Smatch would not have printed this warning about inconsistent NULL
checks).

f7b422b17ee5ee David Howells     2006-06-09  1062  }
f7b422b17ee5ee David Howells     2006-06-09  1063  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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