Re: [PATCH] smack: allow mount opts setting over filesystems with binary mount data

[Casey Schaufler <casey@schaufler-ca.com>]

On 6/22/2015 3:06 AM, U-CORP\t.vivek wrote:
> From: Vivek Trivedi <t.vivek@samsung.com>
>
> Add support for setting smack mount labels(using smackfsdef, smackfsroot,
> smackfshat, smackfsfloor, smackfstransmute) for filesystems with binary
> mount data like NFS.
>
> To achieve this, implement sb_parse_opts_str and sb_set_mnt_opts security
> operations in smack LSM similar to SELinux.
>
> Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>

Acked-by: Casey Schaufler <casey@schaufler-ca.com>

Applied to https://github.com/cschaufler/smack-next.git#smack-for-4.3


> ---
>  security/smack/smack.h     |   18 ++++
>  security/smack/smack_lsm.c |  240 ++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 218 insertions(+), 40 deletions(-)
>
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index 244e035..69ab9eb 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -143,6 +143,24 @@ struct smack_onlycap {
>  	struct smack_known	*smk_label;
>  };
>  
> +/* Super block security struct flags for mount options */
> +#define FSDEFAULT_MNT	0x01
> +#define FSFLOOR_MNT	0x02
> +#define FSHAT_MNT	0x04
> +#define FSROOT_MNT	0x08
> +#define FSTRANS_MNT	0x10
> +
> +#define NUM_SMK_MNT_OPTS	5
> +
> +enum {
> +	Opt_error = -1,
> +	Opt_fsdefault = 1,
> +	Opt_fsfloor = 2,
> +	Opt_fshat = 3,
> +	Opt_fsroot = 4,
> +	Opt_fstransmute = 5,
> +};
> +
>  /*
>   * Mount options
>   */
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index a143328..2d85f78 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -41,6 +41,7 @@
>  #include <linux/msg.h>
>  #include <linux/shm.h>
>  #include <linux/binfmts.h>
> +#include <linux/parser.h>
>  #include "smack.h"
>  
>  #define TRANS_TRUE	"TRUE"
> @@ -64,6 +65,15 @@ static char *smk_bu_mess[] = {
>  	"Unconfined Object",	/* SMACK_UNCONFINED_OBJECT */
>  };
>  
> +static const match_table_t tokens = {
> +	{Opt_fsdefault, SMK_FSDEFAULT "%s"},
> +	{Opt_fsfloor, SMK_FSFLOOR "%s"},
> +	{Opt_fshat, SMK_FSHAT "%s"},
> +	{Opt_fsroot, SMK_FSROOT "%s"},
> +	{Opt_fstransmute, SMK_FSTRANS "%s"},
> +	{Opt_error, NULL},
> +};
> +
>  static void smk_bu_mode(int mode, char *s)
>  {
>  	int i = 0;
> @@ -577,76 +587,192 @@ static int smack_sb_copy_data(char *orig, char *smackopts)
>  }
>  
>  /**
> - * smack_sb_kern_mount - Smack specific mount processing
> + * smack_parse_opts_str - parse Smack specific mount options
> + * @options: mount options string
> + * @opts: where to store converted mount opts
> + *
> + * Returns 0 on success or -ENOMEM on error.
> + *
> + * converts Smack specific mount options to generic security option format
> + */
> +static int smack_parse_opts_str(char *options,
> +		struct security_mnt_opts *opts)
> +{
> +	char *p;
> +	char *fsdefault = NULL, *fsfloor = NULL;
> +	char *fshat = NULL, *fsroot = NULL, *fstransmute = NULL;
> +	int rc = -ENOMEM, num_mnt_opts = 0;
> +
> +	opts->num_mnt_opts = 0;
> +
> +	if (!options)
> +		return 0;
> +
> +	while ((p = strsep(&options, ",")) != NULL) {
> +		int token;
> +		substring_t args[MAX_OPT_ARGS];
> +
> +		if (!*p)
> +			continue;
> +
> +		token = match_token(p, tokens, args);
> +
> +		switch (token) {
> +		case Opt_fsdefault:
> +			if (fsdefault)
> +				goto out_opt_err;
> +			fsdefault = match_strdup(&args[0]);
> +			if (!fsdefault)
> +				goto out_err;
> +			break;
> +		case Opt_fsfloor:
> +			if (fsfloor)
> +				goto out_opt_err;
> +			fsfloor = match_strdup(&args[0]);
> +			if (!fsfloor)
> +				goto out_err;
> +			break;
> +		case Opt_fshat:
> +			if (fshat)
> +				goto out_opt_err;
> +			fshat = match_strdup(&args[0]);
> +			if (!fshat)
> +				goto out_err;
> +			break;
> +		case Opt_fsroot:
> +			if (fsroot)
> +				goto out_opt_err;
> +			fsroot = match_strdup(&args[0]);
> +			if (!fsroot)
> +				goto out_err;
> +			break;
> +		case Opt_fstransmute:
> +			if (fstransmute)
> +				goto out_opt_err;
> +			fstransmute = match_strdup(&args[0]);
> +			if (!fstransmute)
> +				goto out_err;
> +			break;
> +		default:
> +			rc = -EINVAL;
> +			pr_warn("Smack:  unknown mount option\n");
> +			goto out_err;
> +		}
> +	}
> +
> +	opts->mnt_opts = kcalloc(NUM_SMK_MNT_OPTS, sizeof(char *), GFP_ATOMIC);
> +	if (!opts->mnt_opts)
> +		goto out_err;
> +
> +	opts->mnt_opts_flags = kcalloc(NUM_SMK_MNT_OPTS, sizeof(int),
> +			GFP_ATOMIC);
> +	if (!opts->mnt_opts_flags) {
> +		kfree(opts->mnt_opts);
> +		goto out_err;
> +	}
> +
> +	if (fsdefault) {
> +		opts->mnt_opts[num_mnt_opts] = fsdefault;
> +		opts->mnt_opts_flags[num_mnt_opts++] = FSDEFAULT_MNT;
> +	}
> +	if (fsfloor) {
> +		opts->mnt_opts[num_mnt_opts] = fsfloor;
> +		opts->mnt_opts_flags[num_mnt_opts++] = FSFLOOR_MNT;
> +	}
> +	if (fshat) {
> +		opts->mnt_opts[num_mnt_opts] = fshat;
> +		opts->mnt_opts_flags[num_mnt_opts++] = FSHAT_MNT;
> +	}
> +	if (fsroot) {
> +		opts->mnt_opts[num_mnt_opts] = fsroot;
> +		opts->mnt_opts_flags[num_mnt_opts++] = FSROOT_MNT;
> +	}
> +	if (fstransmute) {
> +		opts->mnt_opts[num_mnt_opts] = fstransmute;
> +		opts->mnt_opts_flags[num_mnt_opts++] = FSTRANS_MNT;
> +	}
> +
> +	opts->num_mnt_opts = num_mnt_opts;
> +	return 0;
> +
> +out_opt_err:
> +	rc = -EINVAL;
> +	pr_warn("Smack: duplicate mount options\n");
> +
> +out_err:
> +	kfree(fsdefault);
> +	kfree(fsfloor);
> +	kfree(fshat);
> +	kfree(fsroot);
> +	kfree(fstransmute);
> +	return rc;
> +}
> +
> +/**
> + * smack_set_mnt_opts - set Smack specific mount options
>   * @sb: the file system superblock
> - * @flags: the mount flags
> - * @data: the smack mount options
> + * @opts: Smack mount options
> + * @kern_flags: mount option from kernel space or user space
> + * @set_kern_flags: where to store converted mount opts
>   *
>   * Returns 0 on success, an error code on failure
> + *
> + * Allow filesystems with binary mount data to explicitly set Smack mount
> + * labels.
>   */
> -static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> +static int smack_set_mnt_opts(struct super_block *sb,
> +		struct security_mnt_opts *opts,
> +		unsigned long kern_flags,
> +		unsigned long *set_kern_flags)
>  {
>  	struct dentry *root = sb->s_root;
>  	struct inode *inode = d_backing_inode(root);
>  	struct superblock_smack *sp = sb->s_security;
>  	struct inode_smack *isp;
>  	struct smack_known *skp;
> -	char *op;
> -	char *commap;
> +	int i, num_opts = opts->num_mnt_opts;
>  	int transmute = 0;
> -	int specified = 0;
>  
>  	if (sp->smk_initialized)
>  		return 0;
>  
>  	sp->smk_initialized = 1;
>  
> -	for (op = data; op != NULL; op = commap) {
> -		commap = strchr(op, ',');
> -		if (commap != NULL)
> -			*commap++ = '\0';
> -
> -		if (strncmp(op, SMK_FSHAT, strlen(SMK_FSHAT)) == 0) {
> -			op += strlen(SMK_FSHAT);
> -			skp = smk_import_entry(op, 0);
> +	for (i = 0; i < num_opts; i++) {
> +		switch (opts->mnt_opts_flags[i]) {
> +		case FSDEFAULT_MNT:
> +			skp = smk_import_entry(opts->mnt_opts[i], 0);
>  			if (IS_ERR(skp))
>  				return PTR_ERR(skp);
> -			sp->smk_hat = skp;
> -			specified = 1;
> -
> -		} else if (strncmp(op, SMK_FSFLOOR, strlen(SMK_FSFLOOR)) == 0) {
> -			op += strlen(SMK_FSFLOOR);
> -			skp = smk_import_entry(op, 0);
> +			sp->smk_default = skp;
> +			break;
> +		case FSFLOOR_MNT:
> +			skp = smk_import_entry(opts->mnt_opts[i], 0);
>  			if (IS_ERR(skp))
>  				return PTR_ERR(skp);
>  			sp->smk_floor = skp;
> -			specified = 1;
> -
> -		} else if (strncmp(op, SMK_FSDEFAULT,
> -				   strlen(SMK_FSDEFAULT)) == 0) {
> -			op += strlen(SMK_FSDEFAULT);
> -			skp = smk_import_entry(op, 0);
> +			break;
> +		case FSHAT_MNT:
> +			skp = smk_import_entry(opts->mnt_opts[i], 0);
>  			if (IS_ERR(skp))
>  				return PTR_ERR(skp);
> -			sp->smk_default = skp;
> -			specified = 1;
> -
> -		} else if (strncmp(op, SMK_FSROOT, strlen(SMK_FSROOT)) == 0) {
> -			op += strlen(SMK_FSROOT);
> -			skp = smk_import_entry(op, 0);
> +			sp->smk_hat = skp;
> +			break;
> +		case FSROOT_MNT:
> +			skp = smk_import_entry(opts->mnt_opts[i], 0);
>  			if (IS_ERR(skp))
>  				return PTR_ERR(skp);
>  			sp->smk_root = skp;
> -			specified = 1;
> -
> -		} else if (strncmp(op, SMK_FSTRANS, strlen(SMK_FSTRANS)) == 0) {
> -			op += strlen(SMK_FSTRANS);
> -			skp = smk_import_entry(op, 0);
> +			break;
> +		case FSTRANS_MNT:
> +			skp = smk_import_entry(opts->mnt_opts[i], 0);
>  			if (IS_ERR(skp))
>  				return PTR_ERR(skp);
>  			sp->smk_root = skp;
>  			transmute = 1;
> -			specified = 1;
> +			break;
> +		default:
> +			break;
>  		}
>  	}
>  
> @@ -654,7 +780,7 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
>  		/*
>  		 * Unprivileged mounts don't get to specify Smack values.
>  		 */
> -		if (specified)
> +		if (num_opts)
>  			return -EPERM;
>  		/*
>  		 * Unprivileged mounts get root and default from the caller.
> @@ -663,6 +789,7 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
>  		sp->smk_root = skp;
>  		sp->smk_default = skp;
>  	}
> +
>  	/*
>  	 * Initialize the root inode.
>  	 */
> @@ -682,6 +809,37 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
>  }
>  
>  /**
> + * smack_sb_kern_mount - Smack specific mount processing
> + * @sb: the file system superblock
> + * @flags: the mount flags
> + * @data: the smack mount options
> + *
> + * Returns 0 on success, an error code on failure
> + */
> +static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> +{
> +	int rc = 0;
> +	char *options = data;
> +	struct security_mnt_opts opts;
> +
> +	security_init_mnt_opts(&opts);
> +
> +	if (!options)
> +		goto out;
> +
> +	rc = smack_parse_opts_str(options, &opts);
> +	if (rc)
> +		goto out_err;
> +
> +out:
> +	rc = smack_set_mnt_opts(sb, &opts, 0, NULL);
> +
> +out_err:
> +	security_free_mnt_opts(&opts);
> +	return rc;
> +}
> +
> +/**
>   * smack_sb_statfs - Smack check on statfs
>   * @dentry: identifies the file system in question
>   *
> @@ -4264,6 +4422,8 @@ struct security_hook_list smack_hooks[] = {
>  	LSM_HOOK_INIT(sb_copy_data, smack_sb_copy_data),
>  	LSM_HOOK_INIT(sb_kern_mount, smack_sb_kern_mount),
>  	LSM_HOOK_INIT(sb_statfs, smack_sb_statfs),
> +	LSM_HOOK_INIT(sb_set_mnt_opts, smack_set_mnt_opts),
> +	LSM_HOOK_INIT(sb_parse_opts_str, smack_parse_opts_str),
>  
>  	LSM_HOOK_INIT(bprm_set_creds, smack_bprm_set_creds),
>  	LSM_HOOK_INIT(bprm_committing_creds, smack_bprm_committing_creds),