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Zheng Yejian 7edc3945bd tracing/histograms: Fix memory leak problem This reverts commit `46bbe5c671`. As commit `46bbe5c671` ("tracing: fix double free") said, the "double free" problem reported by clang static analyzer is: > In parse_var_defs() if there is a problem allocating > var_defs.expr, the earlier var_defs.name is freed. > This free is duplicated by free_var_defs() which frees > the rest of the list. However, if there is a problem allocating N-th var_defs.expr: + in parse_var_defs(), the freed 'earlier var_defs.name' is actually the N-th var_defs.name; + then in free_var_defs(), the names from 0th to (N-1)-th are freed; IF ALLOCATING PROBLEM HAPPENED HERE!!! -+ \ \| 0th 1th (N-1)-th N-th V +-------------+-------------+-----+-------------+----------- var_defs: \| name \| expr \| name \| expr \| ... \| name \| expr \| name \| /// +-------------+-------------+-----+-------------+----------- These two frees don't act on same name, so there was no "double free" problem before. Conversely, after that commit, we get a "memory leak" problem because the above "N-th var_defs.name" is not freed. If enable CONFIG_DEBUG_KMEMLEAK and inject a fault at where the N-th var_defs.expr allocated, then execute on shell like: $ echo 'hist:key=call_site:val=$v1,$v2:v1=bytes_req,v2=bytes_alloc' > \ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger Then kmemleak reports: unreferenced object 0xffff8fb100ef3518 (size 8): comm "bash", pid 196, jiffies 4295681690 (age 28.538s) hex dump (first 8 bytes): 76 31 00 00 b1 8f ff ff v1...... backtrace: [<0000000038fe4895>] kstrdup+0x2d/0x60 [<00000000c99c049a>] event_hist_trigger_parse+0x206f/0x20e0 [<00000000ae70d2cc>] trigger_process_regex+0xc0/0x110 [<0000000066737a4c>] event_trigger_write+0x75/0xd0 [<000000007341e40c>] vfs_write+0xbb/0x2a0 [<0000000087fde4c2>] ksys_write+0x59/0xd0 [<00000000581e9cdf>] do_syscall_64+0x3a/0x80 [<00000000cf3b065c>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 Link: https://lkml.kernel.org/r/20220711014731.69520-1-zhengyejian1@huawei.com Cc: stable@vger.kernel.org Fixes: `46bbe5c671` ("tracing: fix double free") Reported-by: Hulk Robot <hulkci@huawei.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>		2022-07-12 16:35:42 -04:00
arch	parisc architecture fixes for kernel v5.19-rc5:	2022-07-02 10:23:36 -07:00
block	block: remove WARN_ON() from bd_link_disk_holder	2022-06-23 07:48:05 -06:00
certs	Certs changes	2022-06-21 12:13:53 -05:00
crypto	Certs changes	2022-06-21 12:13:53 -05:00
Documentation	A NULL pointer dereference fix for vc4, and 3 patches to improve the	2022-07-01 09:27:55 +10:00
drivers	libnvdimm fixes for v5.19-rc5	2022-07-01 16:58:19 -07:00
fs	Fixes for 5.19-rc5:	2022-07-03 09:42:17 -07:00
include	lockref: remove unused 'lockref_get_or_lock()' function	2022-07-03 14:40:28 -07:00
init	gcc-12: disable '-Warray-bounds' universally for now	2022-06-09 10:11:12 -07:00
ipc	These changes update the ipc sysctls so that they are fundamentally	2022-06-03 15:54:57 -07:00
kernel	tracing/histograms: Fix memory leak problem	2022-07-12 16:35:42 -04:00
lib	lockref: remove unused 'lockref_get_or_lock()' function	2022-07-03 14:40:28 -07:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	Minor things, mainly - mailmap updates, MAINTAINERS updates, etc.	2022-06-26 14:00:55 -07:00
net	Notable regression fixes:	2022-07-02 11:20:56 -07:00
samples	fprobe, samples: Add use_trace option and show hit/missed counter	2022-06-17 21:53:29 +02:00
scripts	kbuild: Ignore __this_module in gen_autoksyms.sh	2022-06-26 06:15:05 +09:00
security	selinux: free contexts previously transferred in selinux_add_opt()	2022-06-15 21:20:45 -04:00
sound	sound fixes for 5.19-rc4	2022-06-23 08:44:00 -05:00
tools	perf tools fixes for v5.19: 3rd batch	2022-07-02 09:28:36 -07:00
usr	Not a lot of material this cycle. Many singleton patches against various	2022-05-27 11:22:03 -07:00
virt	KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un\|}blocking	2022-06-09 10:52:20 -04:00
.clang-format	clang-format: Fix space after for_each macros	2022-05-20 19:27:16 +02:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	kbuild: split the second line of .mod into .usyms	2022-05-08 03:16:59 +09:00
.mailmap	mailmap: add entry for Christian Marangi	2022-06-16 19:11:32 -07:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: replace a Microchip AT91 maintainer	2022-02-09 11:30:01 +01:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	Two small fixes	2022-07-01 10:01:32 -07:00
Makefile	Linux 5.19-rc5	2022-07-03 15:39:28 -07:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

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.