mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-28 23:24:50 +00:00
tracing/synthetic: Fix races on freeing last_cmd
commit4ccf11c4e8
upstream. Currently, the "last_cmd" variable can be accessed by multiple processes asynchronously when multiple users manipulate synthetic_events node at the same time, it could lead to use-after-free or double-free. This patch add "lastcmd_mutex" to prevent "last_cmd" from being accessed asynchronously. ================================================================ It's easy to reproduce in the KASAN environment by running the two scripts below in different shells. script 1: while : do echo -n -e '\x88' > /sys/kernel/tracing/synthetic_events done script 2: while : do echo -n -e '\xb0' > /sys/kernel/tracing/synthetic_events done ================================================================ double-free scenario: process A process B ------------------- --------------- 1.kstrdup last_cmd 2.free last_cmd 3.free last_cmd(double-free) ================================================================ use-after-free scenario: process A process B ------------------- --------------- 1.kstrdup last_cmd 2.free last_cmd 3.tracing_log_err(use-after-free) ================================================================ Appendix 1. KASAN report double-free: BUG: KASAN: double-free in kfree+0xdc/0x1d4 Free of addr ***** by task sh/4879 Call trace: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x60/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Allocated by task 4879: ... kstrdup+0x5c/0x98 create_or_delete_synth_event+0x6c/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Freed by task 5464: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x60/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... ================================================================ Appendix 2. KASAN report use-after-free: BUG: KASAN: use-after-free in strlen+0x5c/0x7c Read of size 1 at addr ***** by task sh/5483 sh: CPU: 7 PID: 5483 Comm: sh ... __asan_report_load1_noabort+0x34/0x44 strlen+0x5c/0x7c tracing_log_err+0x60/0x444 create_or_delete_synth_event+0xc4/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Allocated by task 5483: ... kstrdup+0x5c/0x98 create_or_delete_synth_event+0x80/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Freed by task 5480: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x74/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Link: https://lore.kernel.org/linux-trace-kernel/20230321110444.1587-1-Tze-nan.Wu@mediatek.com Fixes:27c888da98
("tracing: Remove size restriction on synthetic event cmd error logging") Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> Cc: "Tom Zanussi" <zanussi@kernel.org> Signed-off-by: Tze-nan Wu <Tze-nan.Wu@mediatek.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
101e8e6bba
commit
9fe183f659
1 changed files with 16 additions and 5 deletions
|
@ -44,14 +44,21 @@ enum { ERRORS };
|
||||||
|
|
||||||
static const char *err_text[] = { ERRORS };
|
static const char *err_text[] = { ERRORS };
|
||||||
|
|
||||||
|
DEFINE_MUTEX(lastcmd_mutex);
|
||||||
static char *last_cmd;
|
static char *last_cmd;
|
||||||
|
|
||||||
static int errpos(const char *str)
|
static int errpos(const char *str)
|
||||||
{
|
{
|
||||||
if (!str || !last_cmd)
|
int ret = 0;
|
||||||
return 0;
|
|
||||||
|
|
||||||
return err_pos(last_cmd, str);
|
mutex_lock(&lastcmd_mutex);
|
||||||
|
if (!str || !last_cmd)
|
||||||
|
goto out;
|
||||||
|
|
||||||
|
ret = err_pos(last_cmd, str);
|
||||||
|
out:
|
||||||
|
mutex_unlock(&lastcmd_mutex);
|
||||||
|
return ret;
|
||||||
}
|
}
|
||||||
|
|
||||||
static void last_cmd_set(const char *str)
|
static void last_cmd_set(const char *str)
|
||||||
|
@ -59,18 +66,22 @@ static void last_cmd_set(const char *str)
|
||||||
if (!str)
|
if (!str)
|
||||||
return;
|
return;
|
||||||
|
|
||||||
|
mutex_lock(&lastcmd_mutex);
|
||||||
kfree(last_cmd);
|
kfree(last_cmd);
|
||||||
|
|
||||||
last_cmd = kstrdup(str, GFP_KERNEL);
|
last_cmd = kstrdup(str, GFP_KERNEL);
|
||||||
|
mutex_unlock(&lastcmd_mutex);
|
||||||
}
|
}
|
||||||
|
|
||||||
static void synth_err(u8 err_type, u16 err_pos)
|
static void synth_err(u8 err_type, u16 err_pos)
|
||||||
{
|
{
|
||||||
|
mutex_lock(&lastcmd_mutex);
|
||||||
if (!last_cmd)
|
if (!last_cmd)
|
||||||
return;
|
goto out;
|
||||||
|
|
||||||
tracing_log_err(NULL, "synthetic_events", last_cmd, err_text,
|
tracing_log_err(NULL, "synthetic_events", last_cmd, err_text,
|
||||||
err_type, err_pos);
|
err_type, err_pos);
|
||||||
|
out:
|
||||||
|
mutex_unlock(&lastcmd_mutex);
|
||||||
}
|
}
|
||||||
|
|
||||||
static int create_synth_event(const char *raw_command);
|
static int create_synth_event(const char *raw_command);
|
||||||
|
|
Loading…
Reference in a new issue