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a12754a8f5
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Steven Rostedt (Google) a12754a8f5 ftrace: Fix modification of direct_function hash while in use 
commit d05cb47066 upstream.

Masami Hiramatsu reported a memory leak in register_ftrace_direct() where
if the number of new entries are added is large enough to cause two
allocations in the loop:

        for (i = 0; i < size; i++) {
                hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
                        new = ftrace_add_rec_direct(entry->ip, addr, &free_hash);
                        if (!new)
                                goto out_remove;
                        entry->direct = addr;
                }
        }

Where ftrace_add_rec_direct() has:

        if (ftrace_hash_empty(direct_functions) ||
            direct_functions->count > 2 * (1 << direct_functions->size_bits)) {
                struct ftrace_hash *new_hash;
                int size = ftrace_hash_empty(direct_functions) ? 0 :
                        direct_functions->count + 1;

                if (size < 32)
                        size = 32;

                new_hash = dup_hash(direct_functions, size);
                if (!new_hash)
                        return NULL;

                *free_hash = direct_functions;
                direct_functions = new_hash;
        }

The "*free_hash = direct_functions;" can happen twice, losing the previous
allocation of direct_functions.

But this also exposed a more serious bug.

The modification of direct_functions above is not safe. As
direct_functions can be referenced at any time to find what direct caller
it should call, the time between:

                new_hash = dup_hash(direct_functions, size);
 and
                direct_functions = new_hash;

can have a race with another CPU (or even this one if it gets interrupted),
and the entries being moved to the new hash are not referenced.

That's because the "dup_hash()" is really misnamed and is really a
"move_hash()". It moves the entries from the old hash to the new one.

Now even if that was changed, this code is not proper as direct_functions
should not be updated until the end. That is the best way to handle
function reference changes, and is the way other parts of ftrace handles
this.

The following is done:

 1. Change add_hash_entry() to return the entry it created and inserted
    into the hash, and not just return success or not.

 2. Replace ftrace_add_rec_direct() with add_hash_entry(), and remove
    the former.

 3. Allocate a "new_hash" at the start that is made for holding both the
    new hash entries as well as the existing entries in direct_functions.

 4. Copy (not move) the direct_function entries over to the new_hash.

 5. Copy the entries of the added hash to the new_hash.

 6. If everything succeeds, then use rcu_pointer_assign() to update the
    direct_functions with the new_hash.

This simplifies the code and fixes both the memory leak as well as the
race condition mentioned above.

Link: https://lore.kernel.org/all/170368070504.42064.8960569647118388081.stgit@devnote2/
Link: https://lore.kernel.org/linux-trace-kernel/20231229115134.08dd5174@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes: 763e34e74b ("ftrace: Add register_ftrace_direct()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-01-05 15:19:44 +01:00
arch kexec: fix KEXEC_FILE dependencies 2024-01-05 15:19:41 +01:00
block blk-cgroup: bypass blkcg_deactivate_policy after destroying 2023-12-20 17:01:55 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: pcrypt - Fix hungtask for PADATA_RESET 2023-11-28 17:19:42 +00:00
Documentation dt-bindings: nvmem: mxs-ocotp: Document fsl,ocotp 2024-01-01 12:42:42 +00:00
drivers Revert "nvme-fc: fix race between error recovery and creating association" 2024-01-05 15:19:43 +01:00
fs ksmbd: fix slab-out-of-bounds in smb_strndup_from_utf16() 2024-01-05 15:19:42 +01:00
include block: renumber QUEUE_FLAG_HW_WC 2024-01-05 15:19:42 +01:00
init proc: sysctl: prevent aliased sysctls from getting passed to init 2023-11-28 17:19:57 +00:00
io_uring io_uring/cmd: fix breakage in SOCKET_URING_OP_SIOC* implementation 2023-12-20 17:01:52 +01:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel ftrace: Fix modification of direct_function hash while in use 2024-01-05 15:19:44 +01:00
lib maple_tree: do not preallocate nodes for slot stores 2024-01-05 15:19:43 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/memory-failure: check the mapcount of the precise page 2024-01-05 15:19:43 +01:00
net mptcp: fix inconsistent state on fastopen race 2024-01-05 15:19:42 +01:00
rust rust: docs: fix logo replacement 2023-10-19 16:40:00 +02:00
samples samples/bpf: syscall_tp_user: Fix array out-of-bound access 2023-11-28 17:19:48 +00:00
scripts scripts/checkstack.pl: match all stack sizes for s390 2023-12-20 17:01:59 +01:00
security keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry 2024-01-01 12:42:33 +00:00
sound ASoC: tas2781: check the validity of prm_no/cfg_no 2024-01-01 12:42:40 +00:00
tools selftests: secretmem: floor the memory size to the multiple of page_size 2024-01-05 15:19:43 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS Char/Misc driver fixes for 6.6-final 2023-10-28 07:51:27 -10:00
Makefile Linux 6.6.9 2024-01-01 12:42:47 +00:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.