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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-06-27 21:18:19 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-06-28 14:21:25 -0400 |
| commit | 39611265edc1af3d574178202e19c31e187e7cf2 (patch) | |
| tree | 5a2fb0590d8da026037129d73500754edceedbc8 /arch/x86/kernel/ftrace.c | |
| parent | d5b844a2cf507fc7642c9ae80a9d585db3065c28 (diff) | |
| download | lwn-39611265edc1af3d574178202e19c31e187e7cf2.tar.gz lwn-39611265edc1af3d574178202e19c31e187e7cf2.zip | |
ftrace/x86: Add a comment to why we take text_mutex in ftrace_arch_code_modify_prepare()
Taking the text_mutex in ftrace_arch_code_modify_prepare() is to fix a
race against module loading and live kernel patching that might try to
change the text permissions while ftrace has it as read/write. This
really needs to be documented in the code. Add a comment that does such.
Link: http://lkml.kernel.org/r/20190627211819.5a591f52@gandalf.local.home
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 33786044d5ac..d7e93b2783fd 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -36,6 +36,11 @@ int ftrace_arch_code_modify_prepare(void) { + /* + * Need to grab text_mutex to prevent a race from module loading + * and live kernel patching from changing the text permissions while + * ftrace has it set to "read/write". + */ mutex_lock(&text_mutex); set_kernel_text_rw(); set_all_modules_text_rw(); |