6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Howells dhowells@redhat.com
[ 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@redhat.com Signed-off-by: Jeff Layton jlayton@kernel.org Link: https://lore.kernel.org/r/165962680944.3334508.6610023900349142034.stgit@war... # v1 Link: https://lore.kernel.org/r/165962729225.3357250.14350728846471527137.stgit@wa... # v2 Link: https://lore.kernel.org/r/165970659095.2812394.6868894171102318796.stgit@war... # v3 Link: https://lore.kernel.org/r/166133579016.3678898.6283195019480567275.stgit@war... # v4 Link: https://lore.kernel.org/r/217595.1662033775@warthog.procyon.org.uk/ # 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@kernel.org Acked-by: Casey Schaufler casey@schaufler-ca.com Acked-by: "Christian Brauner (Microsoft)" brauner@kernel.org Acked-by: Paul Moore paul@paul-moore.com Reviewed-by: Jeff Layton jlayton@kernel.org Message-Id: 20230808-master-v9-1-e0ecde888221@kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 7308a1a7599b4..af796986baee6 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 32828502f09ea..bac98ea18f78b 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 b720424ca37d9..549104a447e36 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 d06e350fedee5..afd6637440418 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2745,6 +2745,27 @@ 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) { @@ -7182,6 +7203,7 @@ 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 6e270cf3fd30c..a8201cf22f20b 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. @@ -4876,6 +4926,7 @@ 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),