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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt15
-rw-r--r--fs/debugfs/inode.c39
-rw-r--r--fs/debugfs/internal.h14
-rw-r--r--lib/Kconfig.debug32
4 files changed, 100 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb95fad81c79..6766a308ad96 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -827,6 +827,21 @@
useful to also enable the page_owner functionality.
on: enable the feature
+ debugfs= [KNL] This parameter enables what is exposed to userspace
+ and debugfs internal clients.
+ Format: { on, no-mount, off }
+ on: All functions are enabled.
+ no-mount:
+ Filesystem is not registered but kernel clients can
+ access APIs and a crashkernel can be used to read
+ its content. There is nothing to mount.
+ off: Filesystem is not registered and clients
+ get a -EPERM as result when trying to register files
+ or directories within debugfs.
+ This is equivalent of the runtime functionality if
+ debugfs was not enabled in the kernel at all.
+ Default value is set in build-time with a kernel configuration.
+
debugpat [X86] Enable PAT debugging
decnet.addr= [HW,NET]
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index b7f2e971ecbc..2fcf66473436 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -35,6 +35,7 @@
static struct vfsmount *debugfs_mount;
static int debugfs_mount_count;
static bool debugfs_registered;
+static unsigned int debugfs_allow = DEFAULT_DEBUGFS_ALLOW_BITS;
/*
* Don't allow access attributes to be changed whilst the kernel is locked down
@@ -266,6 +267,9 @@ static struct dentry *debug_mount(struct file_system_type *fs_type,
int flags, const char *dev_name,
void *data)
{
+ if (!(debugfs_allow & DEBUGFS_ALLOW_API))
+ return ERR_PTR(-EPERM);
+
return mount_single(fs_type, flags, data, debug_fill_super);
}
@@ -311,6 +315,9 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
struct dentry *dentry;
int error;
+ if (!(debugfs_allow & DEBUGFS_ALLOW_API))
+ return ERR_PTR(-EPERM);
+
pr_debug("creating file '%s'\n", name);
if (IS_ERR(parent))
@@ -385,6 +392,11 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
if (IS_ERR(dentry))
return dentry;
+ if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+ failed_creating(dentry);
+ return ERR_PTR(-EPERM);
+ }
+
inode = debugfs_get_inode(dentry->d_sb);
if (unlikely(!inode)) {
pr_err("out of free dentries, can not create file '%s'\n",
@@ -541,6 +553,11 @@ struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
if (IS_ERR(dentry))
return dentry;
+ if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+ failed_creating(dentry);
+ return ERR_PTR(-EPERM);
+ }
+
inode = debugfs_get_inode(dentry->d_sb);
if (unlikely(!inode)) {
pr_err("out of free dentries, can not create directory '%s'\n",
@@ -583,6 +600,11 @@ struct dentry *debugfs_create_automount(const char *name,
if (IS_ERR(dentry))
return dentry;
+ if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+ failed_creating(dentry);
+ return ERR_PTR(-EPERM);
+ }
+
inode = debugfs_get_inode(dentry->d_sb);
if (unlikely(!inode)) {
pr_err("out of free dentries, can not create automount '%s'\n",
@@ -786,10 +808,27 @@ bool debugfs_initialized(void)
}
EXPORT_SYMBOL_GPL(debugfs_initialized);
+static int __init debugfs_kernel(char *str)
+{
+ if (str) {
+ if (!strcmp(str, "on"))
+ debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
+ else if (!strcmp(str, "no-mount"))
+ debugfs_allow = DEBUGFS_ALLOW_API;
+ else if (!strcmp(str, "off"))
+ debugfs_allow = 0;
+ }
+
+ return 0;
+}
+early_param("debugfs", debugfs_kernel);
static int __init debugfs_init(void)
{
int retval;
+ if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
+ return -EPERM;
+
retval = sysfs_create_mount_point(kernel_kobj, "debug");
if (retval)
return retval;
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index 034e6973cead..92af8ae31313 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -29,4 +29,18 @@ struct debugfs_fsdata {
*/
#define DEBUGFS_FSDATA_IS_REAL_FOPS_BIT BIT(0)
+/* Access BITS */
+#define DEBUGFS_ALLOW_API BIT(0)
+#define DEBUGFS_ALLOW_MOUNT BIT(1)
+
+#ifdef CONFIG_DEBUG_FS_ALLOW_ALL
+#define DEFAULT_DEBUGFS_ALLOW_BITS (DEBUGFS_ALLOW_MOUNT | DEBUGFS_ALLOW_API)
+#endif
+#ifdef CONFIG_DEBUG_FS_DISALLOW_MOUNT
+#define DEFAULT_DEBUGFS_ALLOW_BITS (DEBUGFS_ALLOW_API)
+#endif
+#ifdef CONFIG_DEBUG_FS_ALLOW_NONE
+#define DEFAULT_DEBUGFS_ALLOW_BITS (0)
+#endif
+
#endif /* _DEBUGFS_INTERNAL_H_ */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2bff6315224d..256e4ce65f1a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -476,6 +476,38 @@ config DEBUG_FS
If unsure, say N.
+choice
+ prompt "Debugfs default access"
+ depends on DEBUG_FS
+ default DEBUG_FS_ALLOW_ALL
+ help
+ This selects the default access restrictions for debugfs.
+ It can be overridden with kernel command line option
+ debugfs=[on,no-mount,off]. The restrictions apply for API access
+ and filesystem registration.
+
+config DEBUG_FS_ALLOW_ALL
+ bool "Access normal"
+ help
+ No restrictions apply. Both API and filesystem registration
+ is on. This is the normal default operation.
+
+config DEBUG_FS_DISALLOW_MOUNT
+ bool "Do not register debugfs as filesystem"
+ help
+ The API is open but filesystem is not loaded. Clients can still do
+ their work and read with debug tools that do not need
+ debugfs filesystem.
+
+config DEBUG_FS_ALLOW_NONE
+ bool "No access"
+ help
+ Access is off. Clients get -PERM when trying to create nodes in
+ debugfs tree and debugfs is not registered as a filesystem.
+ Client can then back-off or continue without debugfs access.
+
+endchoice
+
source "lib/Kconfig.kgdb"
source "lib/Kconfig.ubsan"