| Message ID | 20230610075738.3273764-3-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | evm: Do HMAC of multiple per LSM xattrs for new inodes | expand |
On 6/10/2023 12:57 AM, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > With the newly added ability of LSMs to supply multiple xattrs, set > SMACK64TRASMUTE in smack_inode_init_security(), instead of d_instantiate(). > Do it by incrementing SMACK_INODE_INIT_XATTRS to 2 and by calling > lsm_get_xattr_slot() a second time, if the transmuting conditions are met. > > The LSM infrastructure passes all xattrs provided by LSMs to the > filesystems through the initxattrs() callback, so that filesystems can > store xattrs in the disk. > > After the change, the SMK_INODE_TRANSMUTE inode flag is always set by > d_instantiate() after fetching SMACK64TRANSMUTE from the disk. Before it > was done by smack_inode_post_setxattr() as result of the __vfs_setxattr() > call. > > Removing __vfs_setxattr() also prevents invalidating the EVM HMAC, by > adding a new xattr without checking and updating the existing HMAC. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com> > --- > security/smack/smack.h | 2 +- > security/smack/smack_lsm.c | 45 ++++++++++++++++++++++++-------------- > 2 files changed, 29 insertions(+), 18 deletions(-) > > diff --git a/security/smack/smack.h b/security/smack/smack.h > index aa15ff56ed6..041688e5a77 100644 > --- a/security/smack/smack.h > +++ b/security/smack/smack.h > @@ -128,7 +128,7 @@ struct task_smack { > > #define SMK_INODE_INSTANT 0x01 /* inode is instantiated */ > #define SMK_INODE_TRANSMUTE 0x02 /* directory is transmuting */ > -#define SMK_INODE_CHANGED 0x04 /* smack was transmuted */ > +#define SMK_INODE_CHANGED 0x04 /* smack was transmuted (unused) */ > #define SMK_INODE_IMPURE 0x08 /* involved in an impure transaction */ > > /* > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 25ade3819af..679156601a1 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -52,7 +52,14 @@ > #define SMK_RECEIVING 1 > #define SMK_SENDING 2 > > -#define SMACK_INODE_INIT_XATTRS 1 > +/* > + * Smack uses multiple xattrs. > + * SMACK64 - for access control, > + * SMACK64TRANSMUTE - label initialization, > + * Not saved on files - SMACK64IPIN and SMACK64IPOUT, > + * Must be set explicitly - SMACK64EXEC and SMACK64MMAP > + */ > +#define SMACK_INODE_INIT_XATTRS 2 > > #ifdef SMACK_IPV6_PORT_LABELING > static DEFINE_MUTEX(smack_ipv6_lock); > @@ -935,7 +942,6 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, > struct xattr *xattrs, int *xattr_count) > { > struct task_smack *tsp = smack_cred(current_cred()); > - struct inode_smack *issp = smack_inode(inode); > struct smack_known *skp = smk_of_task(tsp); > struct smack_known *isp = smk_of_inode(inode); > struct smack_known *dsp = smk_of_inode(dir); > @@ -963,6 +969,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, > if ((tsp->smk_task == tsp->smk_transmuted) || > (may > 0 && ((may & MAY_TRANSMUTE) != 0) && > smk_inode_transmutable(dir))) { > + struct xattr *xattr_transmute; > + > /* > * The caller of smack_dentry_create_files_as() > * should have overridden the current cred, so the > @@ -971,7 +979,18 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, > */ > if (tsp->smk_task != tsp->smk_transmuted) > isp = dsp; > - issp->smk_flags |= SMK_INODE_CHANGED; > + xattr_transmute = lsm_get_xattr_slot(xattrs, > + xattr_count); > + if (xattr_transmute) { > + xattr_transmute->value = kmemdup(TRANS_TRUE, > + TRANS_TRUE_SIZE, > + GFP_NOFS); > + if (!xattr_transmute->value) > + return -ENOMEM; > + > + xattr_transmute->value_len = TRANS_TRUE_SIZE; > + xattr_transmute->name = XATTR_SMACK_TRANSMUTE; > + } > } > > xattr->value = kstrdup(isp->smk_known, GFP_NOFS); > @@ -3518,20 +3537,12 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode) > * If there is a transmute attribute on the > * directory mark the inode. > */ > - if (isp->smk_flags & SMK_INODE_CHANGED) { > - isp->smk_flags &= ~SMK_INODE_CHANGED; > - rc = __vfs_setxattr(&nop_mnt_idmap, dp, inode, > - XATTR_NAME_SMACKTRANSMUTE, > - TRANS_TRUE, TRANS_TRUE_SIZE, > - 0); > - } else { > - rc = __vfs_getxattr(dp, inode, > - XATTR_NAME_SMACKTRANSMUTE, trattr, > - TRANS_TRUE_SIZE); > - if (rc >= 0 && strncmp(trattr, TRANS_TRUE, > - TRANS_TRUE_SIZE) != 0) > - rc = -EINVAL; > - } > + rc = __vfs_getxattr(dp, inode, > + XATTR_NAME_SMACKTRANSMUTE, trattr, > + TRANS_TRUE_SIZE); > + if (rc >= 0 && strncmp(trattr, TRANS_TRUE, > + TRANS_TRUE_SIZE) != 0) > + rc = -EINVAL; > if (rc >= 0) > transflag = SMK_INODE_TRANSMUTE; > }
diff --git a/security/smack/smack.h b/security/smack/smack.h index aa15ff56ed6..041688e5a77 100644 --- a/security/smack/smack.h +++ b/security/smack/smack.h @@ -128,7 +128,7 @@ struct task_smack { #define SMK_INODE_INSTANT 0x01 /* inode is instantiated */ #define SMK_INODE_TRANSMUTE 0x02 /* directory is transmuting */ -#define SMK_INODE_CHANGED 0x04 /* smack was transmuted */ +#define SMK_INODE_CHANGED 0x04 /* smack was transmuted (unused) */ #define SMK_INODE_IMPURE 0x08 /* involved in an impure transaction */ /* diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 25ade3819af..679156601a1 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -52,7 +52,14 @@ #define SMK_RECEIVING 1 #define SMK_SENDING 2 -#define SMACK_INODE_INIT_XATTRS 1 +/* + * Smack uses multiple xattrs. + * SMACK64 - for access control, + * SMACK64TRANSMUTE - label initialization, + * Not saved on files - SMACK64IPIN and SMACK64IPOUT, + * Must be set explicitly - SMACK64EXEC and SMACK64MMAP + */ +#define SMACK_INODE_INIT_XATTRS 2 #ifdef SMACK_IPV6_PORT_LABELING static DEFINE_MUTEX(smack_ipv6_lock); @@ -935,7 +942,6 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, struct xattr *xattrs, int *xattr_count) { struct task_smack *tsp = smack_cred(current_cred()); - struct inode_smack *issp = smack_inode(inode); struct smack_known *skp = smk_of_task(tsp); struct smack_known *isp = smk_of_inode(inode); struct smack_known *dsp = smk_of_inode(dir); @@ -963,6 +969,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, if ((tsp->smk_task == tsp->smk_transmuted) || (may > 0 && ((may & MAY_TRANSMUTE) != 0) && smk_inode_transmutable(dir))) { + struct xattr *xattr_transmute; + /* * The caller of smack_dentry_create_files_as() * should have overridden the current cred, so the @@ -971,7 +979,18 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, */ if (tsp->smk_task != tsp->smk_transmuted) isp = dsp; - issp->smk_flags |= SMK_INODE_CHANGED; + xattr_transmute = lsm_get_xattr_slot(xattrs, + xattr_count); + if (xattr_transmute) { + xattr_transmute->value = kmemdup(TRANS_TRUE, + TRANS_TRUE_SIZE, + GFP_NOFS); + if (!xattr_transmute->value) + return -ENOMEM; + + xattr_transmute->value_len = TRANS_TRUE_SIZE; + xattr_transmute->name = XATTR_SMACK_TRANSMUTE; + } } xattr->value = kstrdup(isp->smk_known, GFP_NOFS); @@ -3518,20 +3537,12 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode) * If there is a transmute attribute on the * directory mark the inode. */ - if (isp->smk_flags & SMK_INODE_CHANGED) { - isp->smk_flags &= ~SMK_INODE_CHANGED; - rc = __vfs_setxattr(&nop_mnt_idmap, dp, inode, - XATTR_NAME_SMACKTRANSMUTE, - TRANS_TRUE, TRANS_TRUE_SIZE, - 0); - } else { - rc = __vfs_getxattr(dp, inode, - XATTR_NAME_SMACKTRANSMUTE, trattr, - TRANS_TRUE_SIZE); - if (rc >= 0 && strncmp(trattr, TRANS_TRUE, - TRANS_TRUE_SIZE) != 0) - rc = -EINVAL; - } + rc = __vfs_getxattr(dp, inode, + XATTR_NAME_SMACKTRANSMUTE, trattr, + TRANS_TRUE_SIZE); + if (rc >= 0 && strncmp(trattr, TRANS_TRUE, + TRANS_TRUE_SIZE) != 0) + rc = -EINVAL; if (rc >= 0) transflag = SMK_INODE_TRANSMUTE; }