linux-kernel - [PATCH] tracing: Zero-initialize parser->buffer to avoid OOB access

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250805151203.1214790-1-pulehui@huaweicloud.com>
Date: Tue,  5 Aug 2025 15:12:03 +0000
From: Pu Lehui <pulehui@...weicloud.com>
To: rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com
Cc: linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH] tracing: Zero-initialize parser->buffer to avoid OOB access

From: Pu Lehui <pulehui@...wei.com>

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 #3 NONE
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
zero-initializing parser->buffer.

Fixes: 8c9af478c06b ("ftrace: Handle commands when closing set_ftrace_filter file")
Signed-off-by: Pu Lehui <pulehui@...wei.com>
---
 kernel/trace/trace.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4283ed4e8f59..97e66cbd3617 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1776,7 +1776,7 @@ int trace_parser_get_init(struct trace_parser *parser, int size)
 {
 	memset(parser, 0, sizeof(*parser));
 
-	parser->buffer = kmalloc(size, GFP_KERNEL);
+	parser->buffer = kzalloc(size, GFP_KERNEL);
 	if (!parser->buffer)
 		return 1;
 
@@ -1860,13 +1860,10 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 
 	/* We either got finished input or we have to wait for another call. */
 	if (isspace(ch) || !ch) {
-		parser->buffer[parser->idx] = 0;
 		parser->cont = false;
 	} else if (parser->idx < parser->size - 1) {
 		parser->cont = true;
 		parser->buffer[parser->idx++] = ch;
-		/* Make sure the parsed string always terminates with '\0'. */
-		parser->buffer[parser->idx] = 0;
 	} else {
 		return -EINVAL;
 	}
-- 
2.34.1