6.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Howells <dhowells@xxxxxxxxxx>
[ Upstream commit d80a8f1b58c2bc8d7c6bfb65401ea4f7ec8cddc2 ]
When NFS superblocks are created by automounting, their LSM parameters
aren't set in the fs_context struct prior to sget_fc() being called,
leading to failure to match existing superblocks.
This bug leads to messages like the following appearing in dmesg when
fscache is enabled:
NFS: Cache volume key already in use (nfs,4.2,2,108,106a8c0,1,,,,100000,100000,2ee,3a98,1d4c,3a98,1)
Fix this by adding a new LSM hook to load fc->security for submount
creation.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Link: https://lore.kernel.org/r/165962680944.3334508.6610023900349142034.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v1
Link: https://lore.kernel.org/r/165962729225.3357250.14350728846471527137.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v2
Link: https://lore.kernel.org/r/165970659095.2812394.6868894171102318796.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v3
Link: https://lore.kernel.org/r/166133579016.3678898.6283195019480567275.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v4
Link: https://lore.kernel.org/r/217595.1662033775@xxxxxxxxxxxxxxxxxxxxxx/ # v5
Fixes: 9bc61ab18b1d ("vfs: Introduce fs_context, switch vfs_kern_mount() to it.")
Fixes: 779df6a5480f ("NFS: Ensure security label is set for root inode")
Tested-by: Jeff Layton <jlayton@xxxxxxxxxx>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Acked-by: "Christian Brauner (Microsoft)" <brauner@xxxxxxxxxx>
Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Message-Id: <20230808-master-v9-1-e0ecde888221@xxxxxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/fs_context.c | 23 +++++++++++++++-
include/linux/lsm_hook_defs.h | 1 +
include/linux/security.h | 6 +++++
security/security.c | 14 ++++++++++
security/selinux/hooks.c | 22 +++++++++++++++
security/smack/smack_lsm.c | 51 +++++++++++++++++++++++++++++++++++
6 files changed, 116 insertions(+), 1 deletion(-)
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 851214d1d013d..375023e40161d 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -315,10 +315,31 @@ struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
}
EXPORT_SYMBOL(fs_context_for_reconfigure);
+/**
+ * fs_context_for_submount: allocate a new fs_context for a submount
+ * @type: file_system_type of the new context
+ * @reference: reference dentry from which to copy relevant info
+ *
+ * Allocate a new fs_context suitable for a submount. This also ensures that
+ * the fc->security object is inherited from @reference (if needed).
+ */
struct fs_context *fs_context_for_submount(struct file_system_type *type,
struct dentry *reference)
{
- return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
+ struct fs_context *fc;
+ int ret;
+
+ fc = alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
+ if (IS_ERR(fc))
+ return fc;
+
+ ret = security_fs_context_submount(fc, reference->d_sb);
+ if (ret) {
+ put_fs_context(fc);
+ return ERR_PTR(ret);
+ }
+
+ return fc;
}
EXPORT_SYMBOL(fs_context_for_submount);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 6bb55e61e8e87..fb9f5f00a7789 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -54,6 +54,7 @@ LSM_HOOK(int, 0, bprm_creds_from_file, struct linux_binprm *bprm, struct file *f
LSM_HOOK(int, 0, bprm_check_security, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committing_creds, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committed_creds, struct linux_binprm *bprm)
+LSM_HOOK(int, 0, fs_context_submount, struct fs_context *fc, struct super_block *reference)
LSM_HOOK(int, 0, fs_context_dup, struct fs_context *fc,
struct fs_context *src_sc)
LSM_HOOK(int, -ENOPARAM, fs_context_parse_param, struct fs_context *fc,
diff --git a/include/linux/security.h b/include/linux/security.h
index e2734e9e44d5c..274c75fa2e272 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -293,6 +293,7 @@ int security_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file);
int security_bprm_check(struct linux_binprm *bprm);
void security_bprm_committing_creds(struct linux_binprm *bprm);
void security_bprm_committed_creds(struct linux_binprm *bprm);
+int security_fs_context_submount(struct fs_context *fc, struct super_block *reference);
int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc);
int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param);
int security_sb_alloc(struct super_block *sb);
@@ -629,6 +630,11 @@ static inline void security_bprm_committed_creds(struct linux_binprm *bprm)
{
}
+static inline int security_fs_context_submount(struct fs_context *fc,
+ struct super_block *reference)
+{
+ return 0;
+}
static inline int security_fs_context_dup(struct fs_context *fc,
struct fs_context *src_fc)
{
diff --git a/security/security.c b/security/security.c
index d5ff7ff45b776..521f74e77dd15 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1138,6 +1138,20 @@ void security_bprm_committed_creds(struct linux_binprm *bprm)
call_void_hook(bprm_committed_creds, bprm);
}
+/**
+ * security_fs_context_submount() - Initialise fc->security
+ * @fc: new filesystem context
+ * @reference: dentry reference for submount/remount
+ *
+ * Fill out the ->security field for a new fs_context.
+ *
+ * Return: Returns 0 on success or negative error code on failure.
+ */
+int security_fs_context_submount(struct fs_context *fc, struct super_block *reference)
+{
+ return call_int_hook(fs_context_submount, 0, fc, reference);
+}
+
/**
* security_fs_context_dup() - Duplicate a fs_context LSM blob
* @fc: destination filesystem context
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 79b4890e9936d..674f43372f490 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2721,6 +2721,27 @@ static int selinux_umount(struct vfsmount *mnt, int flags)
FILESYSTEM__UNMOUNT, NULL);
}
+static int selinux_fs_context_submount(struct fs_context *fc,
+ struct super_block *reference)
+{
+ const struct superblock_security_struct *sbsec;
+ struct selinux_mnt_opts *opts;
+
+ opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+ if (!opts)
+ return -ENOMEM;
+
+ sbsec = selinux_superblock(reference);
+ if (sbsec->flags & FSCONTEXT_MNT)
+ opts->fscontext_sid = sbsec->sid;
+ if (sbsec->flags & CONTEXT_MNT)
+ opts->context_sid = sbsec->mntpoint_sid;
+ if (sbsec->flags & DEFCONTEXT_MNT)
+ opts->defcontext_sid = sbsec->def_sid;
+ fc->security = opts;
+ return 0;
+}
+
static int selinux_fs_context_dup(struct fs_context *fc,
struct fs_context *src_fc)
{
@@ -7142,6 +7163,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
/*
* PUT "CLONING" (ACCESSING + ALLOCATING) HOOKS HERE
*/
+ LSM_HOOK_INIT(fs_context_submount, selinux_fs_context_submount),
LSM_HOOK_INIT(fs_context_dup, selinux_fs_context_dup),
LSM_HOOK_INIT(fs_context_parse_param, selinux_fs_context_parse_param),
LSM_HOOK_INIT(sb_eat_lsm_opts, selinux_sb_eat_lsm_opts),
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 7a3e9ab137d85..6bdc01600aa74 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -614,6 +614,56 @@ static int smack_add_opt(int token, const char *s, void **mnt_opts)
return -EINVAL;
}
+/**
+ * smack_fs_context_submount - Initialise security data for a filesystem context
+ * @fc: The filesystem context.
+ * @reference: reference superblock
+ *
+ * Returns 0 on success or -ENOMEM on error.
+ */
+static int smack_fs_context_submount(struct fs_context *fc,
+ struct super_block *reference)
+{
+ struct superblock_smack *sbsp;
+ struct smack_mnt_opts *ctx;
+ struct inode_smack *isp;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+ fc->security = ctx;
+
+ sbsp = smack_superblock(reference);
+ isp = smack_inode(reference->s_root->d_inode);
+
+ if (sbsp->smk_default) {
+ ctx->fsdefault = kstrdup(sbsp->smk_default->smk_known, GFP_KERNEL);
+ if (!ctx->fsdefault)
+ return -ENOMEM;
+ }
+
+ if (sbsp->smk_floor) {
+ ctx->fsfloor = kstrdup(sbsp->smk_floor->smk_known, GFP_KERNEL);
+ if (!ctx->fsfloor)
+ return -ENOMEM;
+ }
+
+ if (sbsp->smk_hat) {
+ ctx->fshat = kstrdup(sbsp->smk_hat->smk_known, GFP_KERNEL);
+ if (!ctx->fshat)
+ return -ENOMEM;
+ }
+
+ if (isp->smk_flags & SMK_INODE_TRANSMUTE) {
+ if (sbsp->smk_root) {
+ ctx->fstransmute = kstrdup(sbsp->smk_root->smk_known, GFP_KERNEL);
+ if (!ctx->fstransmute)
+ return -ENOMEM;
+ }
+ }
+ return 0;
+}
+
/**
* smack_fs_context_dup - Duplicate the security data on fs_context duplication
* @fc: The new filesystem context.
@@ -4845,6 +4895,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
LSM_HOOK_INIT(ptrace_traceme, smack_ptrace_traceme),
LSM_HOOK_INIT(syslog, smack_syslog),
+ LSM_HOOK_INIT(fs_context_submount, smack_fs_context_submount),
LSM_HOOK_INIT(fs_context_dup, smack_fs_context_dup),
LSM_HOOK_INIT(fs_context_parse_param, smack_fs_context_parse_param),
--
2.40.1
