Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

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

1 files changed, 199 insertions, 0 deletions

diff --git a/Documentation/security/siphash.rst b/Documentation/security/siphash.rst
new file mode 100644
index 000000000..023bd95c7
--- /dev/null
+++ b/Documentation/security/siphash.rst
@@ -0,0 +1,199 @@
+===========================
+SipHash - a short input PRF
+===========================
+
+:Author: Written by Jason A. Donenfeld <jason@zx2c4.com>
+
+SipHash is a cryptographically secure PRF -- a keyed hash function -- that
+performs very well for short inputs, hence the name. It was designed by
+cryptographers Daniel J. Bernstein and Jean-Philippe Aumasson. It is intended
+as a replacement for some uses of: `jhash`, `md5_transform`, `sha1_transform`,
+and so forth.
+
+SipHash takes a secret key filled with randomly generated numbers and either
+an input buffer or several input integers. It spits out an integer that is
+indistinguishable from random. You may then use that integer as part of secure
+sequence numbers, secure cookies, or mask it off for use in a hash table.
+
+Generating a key
+================
+
+Keys should always be generated from a cryptographically secure source of
+random numbers, either using get_random_bytes or get_random_once::
+
+	siphash_key_t key;
+	get_random_bytes(&key, sizeof(key));
+
+If you're not deriving your key from here, you're doing it wrong.
+
+Using the functions
+===================
+
+There are two variants of the function, one that takes a list of integers, and
+one that takes a buffer::
+
+	u64 siphash(const void *data, size_t len, const siphash_key_t *key);
+
+And::
+
+	u64 siphash_1u64(u64, const siphash_key_t *key);
+	u64 siphash_2u64(u64, u64, const siphash_key_t *key);
+	u64 siphash_3u64(u64, u64, u64, const siphash_key_t *key);
+	u64 siphash_4u64(u64, u64, u64, u64, const siphash_key_t *key);
+	u64 siphash_1u32(u32, const siphash_key_t *key);
+	u64 siphash_2u32(u32, u32, const siphash_key_t *key);
+	u64 siphash_3u32(u32, u32, u32, const siphash_key_t *key);
+	u64 siphash_4u32(u32, u32, u32, u32, const siphash_key_t *key);
+
+If you pass the generic siphash function something of a constant length, it
+will constant fold at compile-time and automatically choose one of the
+optimized functions.
+
+Hashtable key function usage::
+
+	struct some_hashtable {
+		DECLARE_HASHTABLE(hashtable, 8);
+		siphash_key_t key;
+	};
+
+	void init_hashtable(struct some_hashtable *table)
+	{
+		get_random_bytes(&table->key, sizeof(table->key));
+	}
+
+	static inline hlist_head *some_hashtable_bucket(struct some_hashtable *table, struct interesting_input *input)
+	{
+		return &table->hashtable[siphash(input, sizeof(*input), &table->key) & (HASH_SIZE(table->hashtable) - 1)];
+	}
+
+You may then iterate like usual over the returned hash bucket.
+
+Security
+========
+
+SipHash has a very high security margin, with its 128-bit key. So long as the
+key is kept secret, it is impossible for an attacker to guess the outputs of
+the function, even if being able to observe many outputs, since 2^128 outputs
+is significant.
+
+Linux implements the "2-4" variant of SipHash.
+
+Struct-passing Pitfalls
+=======================
+
+Often times the XuY functions will not be large enough, and instead you'll
+want to pass a pre-filled struct to siphash. When doing this, it's important
+to always ensure the struct has no padding holes. The easiest way to do this
+is to simply arrange the members of the struct in descending order of size,
+and to use offsetofend() instead of sizeof() for getting the size. For
+performance reasons, if possible, it's probably a good thing to align the
+struct to the right boundary. Here's an example::
+
+	const struct {
+		struct in6_addr saddr;
+		u32 counter;
+		u16 dport;
+	} __aligned(SIPHASH_ALIGNMENT) combined = {
+		.saddr = *(struct in6_addr *)saddr,
+		.counter = counter,
+		.dport = dport
+	};
+	u64 h = siphash(&combined, offsetofend(typeof(combined), dport), &secret);
+
+Resources
+=========
+
+Read the SipHash paper if you're interested in learning more:
+https://131002.net/siphash/siphash.pdf
+
+-------------------------------------------------------------------------------
+
+===============================================
+HalfSipHash - SipHash's insecure younger cousin
+===============================================
+
+:Author: Written by Jason A. Donenfeld <jason@zx2c4.com>
+
+On the off-chance that SipHash is not fast enough for your needs, you might be
+able to justify using HalfSipHash, a terrifying but potentially useful
+possibility. HalfSipHash cuts SipHash's rounds down from "2-4" to "1-3" and,
+even scarier, uses an easily brute-forcable 64-bit key (with a 32-bit output)
+instead of SipHash's 128-bit key. However, this may appeal to some
+high-performance `jhash` users.
+
+HalfSipHash support is provided through the "hsiphash" family of functions.
+
+.. warning::
+   Do not ever use the hsiphash functions except for as a hashtable key
+   function, and only then when you can be absolutely certain that the outputs
+   will never be transmitted out of the kernel. This is only remotely useful
+   over `jhash` as a means of mitigating hashtable flooding denial of service
+   attacks.
+
+On 64-bit kernels, the hsiphash functions actually implement SipHash-1-3, a
+reduced-round variant of SipHash, instead of HalfSipHash-1-3. This is because in
+64-bit code, SipHash-1-3 is no slower than HalfSipHash-1-3, and can be faster.
+Note, this does *not* mean that in 64-bit kernels the hsiphash functions are the
+same as the siphash ones, or that they are secure; the hsiphash functions still
+use a less secure reduced-round algorithm and truncate their outputs to 32
+bits.
+
+Generating a hsiphash key
+=========================
+
+Keys should always be generated from a cryptographically secure source of
+random numbers, either using get_random_bytes or get_random_once::
+
+	hsiphash_key_t key;
+	get_random_bytes(&key, sizeof(key));
+
+If you're not deriving your key from here, you're doing it wrong.
+
+Using the hsiphash functions
+============================
+
+There are two variants of the function, one that takes a list of integers, and
+one that takes a buffer::
+
+	u32 hsiphash(const void *data, size_t len, const hsiphash_key_t *key);
+
+And::
+
+	u32 hsiphash_1u32(u32, const hsiphash_key_t *key);
+	u32 hsiphash_2u32(u32, u32, const hsiphash_key_t *key);
+	u32 hsiphash_3u32(u32, u32, u32, const hsiphash_key_t *key);
+	u32 hsiphash_4u32(u32, u32, u32, u32, const hsiphash_key_t *key);
+
+If you pass the generic hsiphash function something of a constant length, it
+will constant fold at compile-time and automatically choose one of the
+optimized functions.
+
+Hashtable key function usage
+============================
+
+::
+
+	struct some_hashtable {
+		DECLARE_HASHTABLE(hashtable, 8);
+		hsiphash_key_t key;
+	};
+
+	void init_hashtable(struct some_hashtable *table)
+	{
+		get_random_bytes(&table->key, sizeof(table->key));
+	}
+
+	static inline hlist_head *some_hashtable_bucket(struct some_hashtable *table, struct interesting_input *input)
+	{
+		return &table->hashtable[hsiphash(input, sizeof(*input), &table->key) & (HASH_SIZE(table->hashtable) - 1)];
+	}
+
+You may then iterate like usual over the returned hash bucket.
+
+Performance
+===========
+
+hsiphash() is roughly 3 times slower than jhash(). For many replacements, this
+will not be a problem, as the hashtable lookup isn't the bottleneck. And in
+general, this is probably a good sacrifice to make for the security and DoS
+resistance of hsiphash().