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tracing: Limit access to parser->buffer when trace_get_user failed

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When the length of the string written to set_ftrace_filter exceeds
FTRACE_BUFF_MAX, the following KASAN alarm will be triggered:

BUG: KASAN: slab-out-of-bounds in strsep+0x18c/0x1b0
Read of size 1 at addr ffff0000d00bd5ba by task ash/165

CPU: 1 UID: 0 PID: 165 Comm: ash Not tainted 6.16.0-g6bcdbd62bd56-dirty
Hardware name: linux,dummy-virt (DT)
Call trace:
 show_stack+0x34/0x50 (C)
 dump_stack_lvl+0xa0/0x158
 print_address_description.constprop.0+0x88/0x398
 print_report+0xb0/0x280
 kasan_report+0xa4/0xf0
 __asan_report_load1_noabort+0x20/0x30
 strsep+0x18c/0x1b0
 ftrace_process_regex.isra.0+0x100/0x2d8
 ftrace_regex_release+0x484/0x618
 __fput+0x364/0xa58
 ____fput+0x28/0x40
 task_work_run+0x154/0x278
 do_notify_resume+0x1f0/0x220
 el0_svc+0xec/0xf0
 el0t_64_sync_handler+0xa0/0xe8
 el0t_64_sync+0x1ac/0x1b0

The reason is that trace_get_user will fail when processing a string
longer than FTRACE_BUFF_MAX, but not set the end of parser->buffer to 0.
Then an OOB access will be triggered in ftrace_regex_release->
ftrace_process_regex->strsep->strpbrk. We can solve this problem by
limiting access to parser->buffer when trace_get_user failed.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20250813040232.1344527-1-pulehui@huaweicloud.com
Fixes: 8c9af478c0 ("ftrace: Handle commands when closing set_ftrace_filter file")
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Pu Lehui 2025-08-13 04:02:32 +00:00 committed by Steven Rostedt (Google)
parent 7b128f1d53
commit 6a909ea83f
2 changed files with 19 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
kernel/trace/trace.c
View File

@ -1816,7 +1816,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
ret = get_user(ch, ubuf++);
if (ret)
return ret;
goto fail;
read++;
cnt--;
@ -1830,7 +1830,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
while (cnt && isspace(ch)) {
ret = get_user(ch, ubuf++);
if (ret)
return ret;
goto fail;
read++;
cnt--;
}
@ -1848,12 +1848,14 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
while (cnt && !isspace(ch) && ch) {
if (parser->idx < parser->size - 1)
parser->buffer[parser->idx++] = ch;
else
return -EINVAL;
else {
ret = -EINVAL;
goto fail;
}
ret = get_user(ch, ubuf++);
if (ret)
return ret;
goto fail;
read++;
cnt--;
}
@ -1868,11 +1870,15 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
/* Make sure the parsed string always terminates with '\0'. */
parser->buffer[parser->idx] = 0;
} else {
return -EINVAL;
ret = -EINVAL;
goto fail;
}
*ppos += read;
return read;
fail:
trace_parser_fail(parser);
return ret;
}
/* TODO add a seq_buf_to_buffer() */

8
kernel/trace/trace.h
View File

@ -1292,6 +1292,7 @@ bool ftrace_event_is_function(struct trace_event_call *call);
*/
struct trace_parser {
bool cont;
bool fail;
char *buffer;
unsigned idx;
unsigned size;
@ -1299,7 +1300,7 @@ struct trace_parser {
static inline bool trace_parser_loaded(struct trace_parser *parser)
{
return (parser->idx != 0);
return !parser->fail && parser->idx != 0;
}
static inline bool trace_parser_cont(struct trace_parser *parser)
@ -1313,6 +1314,11 @@ static inline void trace_parser_clear(struct trace_parser *parser)
parser->idx = 0;
}
static inline void trace_parser_fail(struct trace_parser *parser)
{
parser->fail = true;
}
extern int trace_parser_get_init(struct trace_parser *parser, int size);
extern void trace_parser_put(struct trace_parser *parser);
extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,