From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- samples/kobject/Makefile | 2 + samples/kobject/kobject-example.c | 145 ++++++++++++++++++ samples/kobject/kset-example.c | 305 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 452 insertions(+) create mode 100644 samples/kobject/Makefile create mode 100644 samples/kobject/kobject-example.c create mode 100644 samples/kobject/kset-example.c (limited to 'samples/kobject') diff --git a/samples/kobject/Makefile b/samples/kobject/Makefile new file mode 100644 index 000000000..bb5d21997 --- /dev/null +++ b/samples/kobject/Makefile @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +obj-$(CONFIG_SAMPLE_KOBJECT) += kobject-example.o kset-example.o diff --git a/samples/kobject/kobject-example.c b/samples/kobject/kobject-example.c new file mode 100644 index 000000000..36f3fbc47 --- /dev/null +++ b/samples/kobject/kobject-example.c @@ -0,0 +1,145 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Sample kobject implementation + * + * Copyright (C) 2004-2007 Greg Kroah-Hartman + * Copyright (C) 2007 Novell Inc. + */ +#include +#include +#include +#include +#include + +/* + * This module shows how to create a simple subdirectory in sysfs called + * /sys/kernel/kobject_example In that directory, 3 files are created: + * "foo", "baz", and "bar". If an integer is written to these files, it can be + * later read out of it. + */ + +static int foo; +static int baz; +static int bar; + +/* + * The "foo" file where a static variable is read from and written to. + */ +static ssize_t foo_show(struct kobject *kobj, const struct kobj_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "%d\n", foo); +} + +static ssize_t foo_store(struct kobject *kobj, const struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int ret; + + ret = kstrtoint(buf, 10, &foo); + if (ret < 0) + return ret; + + return count; +} + +/* Sysfs attributes cannot be world-writable. */ +static const struct kobj_attribute foo_attribute = + __KOBJ_ATTR(foo, 0664, foo_show, foo_store); + +/* + * More complex function where we determine which variable is being accessed by + * looking at the attribute for the "baz" and "bar" files. + */ +static ssize_t b_show(struct kobject *kobj, const struct kobj_attribute *attr, + char *buf) +{ + int var; + + if (strcmp(attr->attr.name, "baz") == 0) + var = baz; + else + var = bar; + return sysfs_emit(buf, "%d\n", var); +} + +static ssize_t b_store(struct kobject *kobj, const struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int var, ret; + + ret = kstrtoint(buf, 10, &var); + if (ret < 0) + return ret; + + if (strcmp(attr->attr.name, "baz") == 0) + baz = var; + else + bar = var; + return count; +} + +static const struct kobj_attribute baz_attribute = + __KOBJ_ATTR(baz, 0664, b_show, b_store); +static const struct kobj_attribute bar_attribute = + __KOBJ_ATTR(bar, 0664, b_show, b_store); + + +/* + * Create a group of attributes so that we can create and destroy them all + * at once. + */ +static const struct attribute *const attrs[] = { + &foo_attribute.attr, + &baz_attribute.attr, + &bar_attribute.attr, + NULL, /* need to NULL terminate the list of attributes */ +}; + +/* + * An unnamed attribute group will put all of the attributes directly in + * the kobject directory. If we specify a name, a subdirectory will be + * created for the attributes with the directory being the name of the + * attribute group. + */ +static const struct attribute_group attr_group = { + .attrs_const = attrs, +}; + +static struct kobject *example_kobj; + +static int __init example_init(void) +{ + int retval; + + /* + * Create a simple kobject with the name of "kobject_example", + * located under /sys/kernel/ + * + * As this is a simple directory, no uevent will be sent to + * userspace. That is why this function should not be used for + * any type of dynamic kobjects, where the name and number are + * not known ahead of time. + */ + example_kobj = kobject_create_and_add("kobject_example", kernel_kobj); + if (!example_kobj) + return -ENOMEM; + + /* Create the files associated with this kobject */ + retval = sysfs_create_group(example_kobj, &attr_group); + if (retval) + kobject_put(example_kobj); + + return retval; +} + +static void __exit example_exit(void) +{ + kobject_put(example_kobj); +} + +module_init(example_init); +module_exit(example_exit); +MODULE_DESCRIPTION("Sample kobject implementation"); +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Greg Kroah-Hartman "); diff --git a/samples/kobject/kset-example.c b/samples/kobject/kset-example.c new file mode 100644 index 000000000..d0103904e --- /dev/null +++ b/samples/kobject/kset-example.c @@ -0,0 +1,305 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Sample kset and ktype implementation + * + * Copyright (C) 2004-2007 Greg Kroah-Hartman + * Copyright (C) 2007 Novell Inc. + */ +#include +#include +#include +#include +#include +#include + +/* + * This module shows how to create a kset in sysfs called + * /sys/kernel/kset_example + * Then three kobjects are created and assigned to this kset, "foo", "baz", + * and "bar". In those kobjects, attributes of the same name are also + * created and if an integer is written to these files, it can be later + * read out of it. + */ + + +/* + * This is our "object" that we will create a few of and register them with + * sysfs. + */ +struct foo_obj { + struct kobject kobj; + int foo; + int baz; + int bar; +}; +#define to_foo_obj(x) container_of(x, struct foo_obj, kobj) + +/* a custom attribute that works just for a struct foo_obj. */ +struct foo_attribute { + struct attribute attr; + ssize_t (*show)(struct foo_obj *foo, const struct foo_attribute *attr, char *buf); + ssize_t (*store)(struct foo_obj *foo, const struct foo_attribute *attr, + const char *buf, size_t count); +}; +#define to_foo_attr(x) container_of_const(x, struct foo_attribute, attr) + +/* + * The default show function that must be passed to sysfs. This will be + * called by sysfs for whenever a show function is called by the user on a + * sysfs file associated with the kobjects we have registered. We need to + * transpose back from a "default" kobject to our custom struct foo_obj and + * then call the show function for that specific object. + */ +static ssize_t foo_attr_show(struct kobject *kobj, + struct attribute *attr, + char *buf) +{ + const struct foo_attribute *attribute; + struct foo_obj *foo; + + attribute = to_foo_attr(attr); + foo = to_foo_obj(kobj); + + if (!attribute->show) + return -EIO; + + return attribute->show(foo, attribute, buf); +} + +/* + * Just like the default show function above, but this one is for when the + * sysfs "store" is requested (when a value is written to a file.) + */ +static ssize_t foo_attr_store(struct kobject *kobj, + struct attribute *attr, + const char *buf, size_t len) +{ + const struct foo_attribute *attribute; + struct foo_obj *foo; + + attribute = to_foo_attr(attr); + foo = to_foo_obj(kobj); + + if (!attribute->store) + return -EIO; + + return attribute->store(foo, attribute, buf, len); +} + +/* Our custom sysfs_ops that we will associate with our ktype later on */ +static const struct sysfs_ops foo_sysfs_ops = { + .show = foo_attr_show, + .store = foo_attr_store, +}; + +/* + * The release function for our object. This is REQUIRED by the kernel to + * have. We free the memory held in our object here. + * + * NEVER try to get away with just a "blank" release function to try to be + * smarter than the kernel. Turns out, no one ever is... + */ +static void foo_release(struct kobject *kobj) +{ + struct foo_obj *foo; + + foo = to_foo_obj(kobj); + kfree(foo); +} + +/* + * The "foo" file where the .foo variable is read from and written to. + */ +static ssize_t foo_show(struct foo_obj *foo_obj, const struct foo_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "%d\n", foo_obj->foo); +} + +static ssize_t foo_store(struct foo_obj *foo_obj, const struct foo_attribute *attr, + const char *buf, size_t count) +{ + int ret; + + ret = kstrtoint(buf, 10, &foo_obj->foo); + if (ret < 0) + return ret; + + return count; +} + +/* Sysfs attributes cannot be world-writable. */ +static const struct foo_attribute foo_attribute = + __ATTR(foo, 0664, foo_show, foo_store); + +/* + * More complex function where we determine which variable is being accessed by + * looking at the attribute for the "baz" and "bar" files. + */ +static ssize_t b_show(struct foo_obj *foo_obj, const struct foo_attribute *attr, + char *buf) +{ + int var; + + if (strcmp(attr->attr.name, "baz") == 0) + var = foo_obj->baz; + else + var = foo_obj->bar; + return sysfs_emit(buf, "%d\n", var); +} + +static ssize_t b_store(struct foo_obj *foo_obj, const struct foo_attribute *attr, + const char *buf, size_t count) +{ + int var, ret; + + ret = kstrtoint(buf, 10, &var); + if (ret < 0) + return ret; + + if (strcmp(attr->attr.name, "baz") == 0) + foo_obj->baz = var; + else + foo_obj->bar = var; + return count; +} + +static const struct foo_attribute baz_attribute = + __ATTR(baz, 0664, b_show, b_store); +static const struct foo_attribute bar_attribute = + __ATTR(bar, 0664, b_show, b_store); + +/* + * Create a group of attributes so that we can create and destroy them all + * at once. + */ +static const struct attribute *const foo_default_attrs[] = { + &foo_attribute.attr, + &baz_attribute.attr, + &bar_attribute.attr, + NULL, /* need to NULL terminate the list of attributes */ +}; + +static umode_t foo_default_attrs_is_visible(struct kobject *kobj, + const struct attribute *attr, + int n) +{ + /* Hide attributes with the same name as the kobject. */ + if (strcmp(kobject_name(kobj), attr->name) == 0) + return 0; + return attr->mode; +} + +static const struct attribute_group foo_default_group = { + .attrs_const = foo_default_attrs, + .is_visible_const = foo_default_attrs_is_visible, +}; +__ATTRIBUTE_GROUPS(foo_default); + +/* + * Our own ktype for our kobjects. Here we specify our sysfs ops, the + * release function, and the set of default attributes we want created + * whenever a kobject of this type is registered with the kernel. + */ +static const struct kobj_type foo_ktype = { + .sysfs_ops = &foo_sysfs_ops, + .release = foo_release, + .default_groups = foo_default_groups, +}; + +static struct kset *example_kset; +static struct foo_obj *foo_obj; +static struct foo_obj *bar_obj; +static struct foo_obj *baz_obj; + +static struct foo_obj *create_foo_obj(const char *name) +{ + struct foo_obj *foo; + int retval; + + /* allocate the memory for the whole object */ + foo = kzalloc(sizeof(*foo), GFP_KERNEL); + if (!foo) + return NULL; + + /* + * As we have a kset for this kobject, we need to set it before calling + * the kobject core. + */ + foo->kobj.kset = example_kset; + + /* + * Initialize and add the kobject to the kernel. All the default files + * will be created here. As we have already specified a kset for this + * kobject, we don't have to set a parent for the kobject, the kobject + * will be placed beneath that kset automatically. + */ + retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); + if (retval) { + kobject_put(&foo->kobj); + return NULL; + } + + /* + * We are always responsible for sending the uevent that the kobject + * was added to the system. + */ + kobject_uevent(&foo->kobj, KOBJ_ADD); + + return foo; +} + +static void destroy_foo_obj(struct foo_obj *foo) +{ + kobject_put(&foo->kobj); +} + +static int __init example_init(void) +{ + /* + * Create a kset with the name of "kset_example", + * located under /sys/kernel/ + */ + example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); + if (!example_kset) + return -ENOMEM; + + /* + * Create three objects and register them with our kset + */ + foo_obj = create_foo_obj("foo"); + if (!foo_obj) + goto foo_error; + + bar_obj = create_foo_obj("bar"); + if (!bar_obj) + goto bar_error; + + baz_obj = create_foo_obj("baz"); + if (!baz_obj) + goto baz_error; + + return 0; + +baz_error: + destroy_foo_obj(bar_obj); +bar_error: + destroy_foo_obj(foo_obj); +foo_error: + kset_unregister(example_kset); + return -EINVAL; +} + +static void __exit example_exit(void) +{ + destroy_foo_obj(baz_obj); + destroy_foo_obj(bar_obj); + destroy_foo_obj(foo_obj); + kset_unregister(example_kset); +} + +module_init(example_init); +module_exit(example_exit); +MODULE_DESCRIPTION("Sample kset and ktype implementation"); +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Greg Kroah-Hartman "); -- cgit v1.3.1