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Mon, 21 Apr 2025 08:28:59 -0700 (PDT) Received: from localhost.localdomain ([121.185.186.233]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3087e04a94bsm7640379a91.40.2025.04.21.08.28.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Apr 2025 08:28:59 -0700 (PDT) From: Jeongjun Park To: rostedt@goodmis.org, mhiramat@kernel.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, syzbot+c8cd2d2c412b868263fb@syzkaller.appspotmail.com, Jeongjun Park Subject: [PATCH v2] tracing: fix oob write in trace_seq_to_buffer() Date: Tue, 22 Apr 2025 00:28:50 +0900 Message-ID: <20250421152850.15387-1-aha310510@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" syzbot reported this bug: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BUG: KASAN: slab-out-of-bounds in trace_seq_to_buffer kernel/trace/trace.c:= 1830 [inline] BUG: KASAN: slab-out-of-bounds in tracing_splice_read_pipe+0x6be/0xdd0 kern= el/trace/trace.c:6822 Write of size 4507 at addr ffff888032b6b000 by task syz.2.320/7260 CPU: 1 UID: 0 PID: 7260 Comm: syz.2.320 Not tainted 6.15.0-rc1-syzkaller-00= 301-g3bde70a2c827 #0 PREEMPT(full)=20 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Goo= gle 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc3/0x670 mm/kasan/report.c:521 kasan_report+0xe0/0x110 mm/kasan/report.c:634 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189 __asan_memcpy+0x3c/0x60 mm/kasan/shadow.c:106 trace_seq_to_buffer kernel/trace/trace.c:1830 [inline] tracing_splice_read_pipe+0x6be/0xdd0 kernel/trace/trace.c:6822 .... =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D It has been reported that trace_seq_to_buffer() tries to copy more data than PAGE_SIZE to buf. Therefore, to prevent this, we should use the smaller of trace_seq_used(&iter->seq) and PAGE_SIZE as an argument. Reported-by: syzbot+c8cd2d2c412b868263fb@syzkaller.appspotmail.com Fixes: 3c56819b14b0 ("tracing: splice support for tracing_pipe") Suggested-by: Steven Rostedt Signed-off-by: Jeongjun Park --- v2: Corrected the correct location as suggested by the maintainer --- kernel/trace/trace.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8ddf6b17215c..170c31da61e0 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6784,7 +6784,7 @@ static ssize_t tracing_splice_read_pipe(struct file *= filp, }; ssize_t ret; size_t rem; - unsigned int i; + unsigned int i, copy_len; =20 if (splice_grow_spd(pipe, &spd)) return -ENOMEM; @@ -6818,16 +6818,18 @@ static ssize_t tracing_splice_read_pipe(struct file= *filp, =20 rem =3D tracing_fill_pipe_page(rem, iter); =20 + copy_len =3D trace_seq_used(&iter->seq); + /* Copy the data into the page, so we can start over. */ ret =3D trace_seq_to_buffer(&iter->seq, page_address(spd.pages[i]), - trace_seq_used(&iter->seq)); + min(copy_len, PAGE_SIZE)); if (ret < 0) { __free_page(spd.pages[i]); break; } spd.partial[i].offset =3D 0; - spd.partial[i].len =3D trace_seq_used(&iter->seq); + spd.partial[i].len =3D min(copy_len, PAGE_SIZE); =20 trace_seq_init(&iter->seq); } --