Identify EVM unsupported filesystems by defining a new flag
SB_I_EVM_UNSUPPORTED.
Don't verify, write, remove or update 'security.evm' on unsupported
filesystems.
Signed-off-by: Mimi Zohar <[email protected]>
---
include/linux/fs.h | 1 +
security/integrity/evm/evm_main.c | 35 ++++++++++++++++++++++++++++++-
2 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98b7a7a8c42e..db9350a734ef 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1164,6 +1164,7 @@ extern int send_sigurg(struct fown_struct *fown);
#define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */
#define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020
#define SB_I_UNTRUSTED_MOUNTER 0x00000040
+#define SB_I_EVM_UNSUPPORTED 0x00000050
#define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */
#define SB_I_PERSB_BDI 0x00000200 /* has a per-sb bdi */
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 02adba635b02..cc7956d7878b 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -151,6 +151,17 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
return count;
}
+static int is_unsupported_fs(struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+
+ if (inode->i_sb->s_iflags & SB_I_EVM_UNSUPPORTED) {
+ pr_info_once("%s not supported\n", inode->i_sb->s_type->name);
+ return 1;
+ }
+ return 0;
+}
+
/*
* evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
*
@@ -181,6 +192,9 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
return iint->evm_status;
+ if (is_unsupported_fs(dentry))
+ return INTEGRITY_UNKNOWN;
+
/* if status is not PASS, try to check again - against -ENOMEM */
/* first need to know the sig type */
@@ -408,6 +422,9 @@ enum integrity_status evm_verifyxattr(struct dentry *dentry,
if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
return INTEGRITY_UNKNOWN;
+ if (is_unsupported_fs(dentry))
+ return INTEGRITY_UNKNOWN;
+
if (!iint) {
iint = integrity_iint_find(d_backing_inode(dentry));
if (!iint)
@@ -491,15 +508,21 @@ static int evm_protect_xattr(struct mnt_idmap *idmap,
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ if (is_unsupported_fs(dentry))
+ return -EPERM;
} else if (!evm_protected_xattr(xattr_name)) {
if (!posix_xattr_acl(xattr_name))
return 0;
+ if (is_unsupported_fs(dentry))
+ return 0;
+
evm_status = evm_verify_current_integrity(dentry);
if ((evm_status == INTEGRITY_PASS) ||
(evm_status == INTEGRITY_NOXATTRS))
return 0;
goto out;
- }
+ } else if (is_unsupported_fs(dentry))
+ return 0;
evm_status = evm_verify_current_integrity(dentry);
if (evm_status == INTEGRITY_NOXATTRS) {
@@ -750,6 +773,9 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
if (!(evm_initialized & EVM_INIT_HMAC))
return;
+ if (is_unsupported_fs(dentry))
+ return;
+
evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
}
@@ -814,8 +840,12 @@ int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;
+ if (is_unsupported_fs(dentry))
+ return 0;
+
if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
return 0;
+
evm_status = evm_verify_current_integrity(dentry);
/*
* Writing attrs is safe for portable signatures, as portable signatures
@@ -859,6 +889,9 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
if (!(evm_initialized & EVM_INIT_HMAC))
return;
+ if (is_unsupported_fs(dentry))
+ return;
+
if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
evm_update_evmxattr(dentry, NULL, NULL, 0);
}
--
2.39.3
On Tue, 2023-12-19 at 12:52 -0500, Mimi Zohar wrote:
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 98b7a7a8c42e..db9350a734ef 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1164,6 +1164,7 @@ extern int send_sigurg(struct fown_struct *fown);
> #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */
> #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020
> #define SB_I_UNTRUSTED_MOUNTER 0x00000040
> +#define SB_I_EVM_UNSUPPORTED 0x00000050
This needs to be fixed.
Mimi
>
> #define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */
> #define SB_I_PERSB_BDI 0x00000200 /* has a per-sb bdi */
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
On Tue, Dec 19, 2023 at 9:10 PM Mimi Zohar <[email protected]> wrote:
>
> On Tue, 2023-12-19 at 12:52 -0500, Mimi Zohar wrote:
>
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 98b7a7a8c42e..db9350a734ef 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -1164,6 +1164,7 @@ extern int send_sigurg(struct fown_struct *fown);
> > #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */
> > #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020
> > #define SB_I_UNTRUSTED_MOUNTER 0x00000040
> > +#define SB_I_EVM_UNSUPPORTED 0x00000050
>
> This needs to be fixed.
>
With this fixed, you may add:
Acked-by: Amir Goldstein <[email protected]>
Thanks,
Amir.