Re: [PATCH v4] selinux: policydb - fix byte order and alignment issues

[Stephen Smalley <sds@tycho.nsa.gov>]

On 10/18/2018 03:47 AM, Ondrej Mosnacek wrote:
> Do the LE conversions before doing the Infiniband-related range checks.
> The incorrect checks are otherwise causing a failure to load any policy
> with an ibendportcon rule on BE systems. This can be reproduced by
> running (on e.g. ppc64):
> 
> cat >my_module.cil <<EOF
> (type test_ibendport_t)
> (roletype object_r test_ibendport_t)
> (ibendportcon mlx4_0 1 (system_u object_r test_ibendport_t ((s0) (s0))))
> EOF
> semodule -i my_module.cil
> 
> Also, fix loading/storing the 64-bit subnet prefix for OCON_IBPKEY to
> use a correctly aligned buffer.
> 
> Finally, do not use the 'nodebuf' (u32) buffer where 'buf' (__le32)
> should be used instead.
> 
> Tested internally on a ppc64 machine with a RHEL 7 kernel with this
> patch applied.
> 
> Cc: Daniel Jurgens <danielj@mellanox.com>
> Cc: Eli Cohen <eli@mellanox.com>
> Cc: James Morris <jmorris@namei.org>
> Cc: Doug Ledford <dledford@redhat.com>
> Cc: <stable@vger.kernel.org> # 4.13+
> Fixes: a806f7a1616f ("selinux: Create policydb version for Infiniband support")
> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
> ---
>   security/selinux/ss/policydb.c | 46 +++++++++++++++++++++++-----------
>   1 file changed, 32 insertions(+), 14 deletions(-)
> 
> Changes in v4:
>   - defer assignment to 16-bit struct fields to after the range check
> 
> Changes in v3:
>   - use separate buffer for the 64-bit subnet_prefix
>   - add comments on the byte ordering of subnet_prefix
>   - deduplicate the le32_to_cpu() calls from checks
> 
> Changes in v2:
>   - add reproducer to commit message
>   - update e-mail address of James Morris
>   - better Cc also the old SELinux ML
> 
> diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
> index f4eadd3f7350..d50668006a52 100644
> --- a/security/selinux/ss/policydb.c
> +++ b/security/selinux/ss/policydb.c
> @@ -2108,6 +2108,7 @@ static int ocontext_read(struct policydb *p, struct policydb_compat_info *info,
>   {
>   	int i, j, rc;
>   	u32 nel, len;
> +	__be64 prefixbuf[1];
>   	__le32 buf[3];
>   	struct ocontext *l, *c;
>   	u32 nodebuf[8];
> @@ -2217,21 +2218,30 @@ static int ocontext_read(struct policydb *p, struct policydb_compat_info *info,
>   					goto out;
>   				break;
>   			}
> -			case OCON_IBPKEY:
> -				rc = next_entry(nodebuf, fp, sizeof(u32) * 4);
> +			case OCON_IBPKEY: {
> +				u32 pkey_lo, pkey_hi;
> +
> +				rc = next_entry(prefixbuf, fp, sizeof(u64));
> +				if (rc)
> +					goto out;
> +
> +				/* we need to have subnet_prefix in CPU order */
> +				c->u.ibpkey.subnet_prefix = be64_to_cpu(prefixbuf[0]);
> +
> +				rc = next_entry(buf, fp, sizeof(u32) * 2);
>   				if (rc)
>   					goto out;
>   
> -				c->u.ibpkey.subnet_prefix = be64_to_cpu(*((__be64 *)nodebuf));
> +				pkey_lo = le32_to_cpu(buf[0]);
> +				pkey_hi = le32_to_cpu(buf[1]);
>   
> -				if (nodebuf[2] > 0xffff ||
> -				    nodebuf[3] > 0xffff) {
> +				if (pkey_lo > U16_MAX || pkey_hi > U16_MAX) {
>   					rc = -EINVAL;
>   					goto out;
>   				}
>   
> -				c->u.ibpkey.low_pkey = le32_to_cpu(nodebuf[2]);
> -				c->u.ibpkey.high_pkey = le32_to_cpu(nodebuf[3]);
> +				c->u.ibpkey.low_pkey  = pkey_lo;
> +				c->u.ibpkey.high_pkey = pkey_hi;
>   
>   				rc = context_read_and_validate(&c->context[0],
>   							       p,
> @@ -2239,6 +2249,7 @@ static int ocontext_read(struct policydb *p, struct policydb_compat_info *info,
>   				if (rc)
>   					goto out;
>   				break;
> +			}
>   			case OCON_IBENDPORT:
>   				rc = next_entry(buf, fp, sizeof(u32) * 2);
>   				if (rc)
> @@ -2249,13 +2260,14 @@ static int ocontext_read(struct policydb *p, struct policydb_compat_info *info,
>   				if (rc)
>   					goto out;
>   
> -				if (buf[1] > 0xff || buf[1] == 0) {
> +				c->u.ibendport.port = le32_to_cpu(buf[1]);

ibendport.port is a u8 here, same issue.

> +
> +				if (c->u.ibendport.port > 0xff ||
> +				    c->u.ibendport.port == 0) {
>   					rc = -EINVAL;
>   					goto out;
>   				}
>   
> -				c->u.ibendport.port = le32_to_cpu(buf[1]);
> -
>   				rc = context_read_and_validate(&c->context[0],
>   							       p,
>   							       fp);
> @@ -3105,6 +3117,7 @@ static int ocontext_write(struct policydb *p, struct policydb_compat_info *info,
>   {
>   	unsigned int i, j, rc;
>   	size_t nel, len;
> +	__be64 prefixbuf[1];
>   	__le32 buf[3];
>   	u32 nodebuf[8];
>   	struct ocontext *c;
> @@ -3192,12 +3205,17 @@ static int ocontext_write(struct policydb *p, struct policydb_compat_info *info,
>   					return rc;
>   				break;
>   			case OCON_IBPKEY:
> -				*((__be64 *)nodebuf) = cpu_to_be64(c->u.ibpkey.subnet_prefix);
> +				/* subnet_prefix is in CPU order */
> +				prefixbuf[0] = cpu_to_be64(c->u.ibpkey.subnet_prefix);
>   
> -				nodebuf[2] = cpu_to_le32(c->u.ibpkey.low_pkey);
> -				nodebuf[3] = cpu_to_le32(c->u.ibpkey.high_pkey);
> +				rc = put_entry(prefixbuf, sizeof(u64), 1, fp);
> +				if (rc)
> +					return rc;
>   
> -				rc = put_entry(nodebuf, sizeof(u32), 4, fp);
> +				buf[0] = cpu_to_le32(c->u.ibpkey.low_pkey);
> +				buf[1] = cpu_to_le32(c->u.ibpkey.high_pkey);
> +
> +				rc = put_entry(buf, sizeof(u32), 2, fp);
>   				if (rc)
>   					return rc;
>   				rc = context_write(p, &c->context[0], fp);
>