From: Arnd Bergmann arnd@arndb.de
[ Upstream commit c344f07aa1b4ba38ca8fabe407a2afe2f436323c ]
Syzbot found that passing ioctl command 0xc0505609 into a 64-bit kernel from a 32-bit process causes uninitialized kernel memory to get passed to drivers instead of the user space data:
BUG: KMSAN: uninit-value in check_array_args drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] BUG: KMSAN: uninit-value in video_usercopy+0x1631/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3315 CPU: 0 PID: 19595 Comm: syz-executor.4 Not tainted 5.11.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x21c/0x280 lib/dump_stack.c:120 kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197 check_array_args drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] video_usercopy+0x1631/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3315 video_ioctl2+0x9f/0xb0 drivers/media/v4l2-core/v4l2-ioctl.c:3391 v4l2_ioctl+0x255/0x290 drivers/media/v4l2-core/v4l2-dev.c:360 v4l2_compat_ioctl32+0x2c6/0x370 drivers/media/v4l2-core/v4l2-compat-ioctl32.c:1248 __do_compat_sys_ioctl fs/ioctl.c:842 [inline] __se_compat_sys_ioctl+0x53d/0x1100 fs/ioctl.c:793 __ia32_compat_sys_ioctl+0x4a/0x70 fs/ioctl.c:793 do_syscall_32_irqs_on arch/x86/entry/common.c:79 [inline] __do_fast_syscall_32+0x102/0x160 arch/x86/entry/common.c:141 do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:166 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:209 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
The time32 commands are defined but were never meant to be called on 64-bit machines, as those have always used time64 interfaces. I missed this in my patch that introduced the time64 handling on 32-bit platforms.
The problem in this case is the mismatch of one function checking for the numeric value of the command and another function checking for the type of process (native vs compat) instead, with the result being that for this combination, nothing gets copied into the buffer at all.
Avoid this by only trying to convert the time32 commands when running on a 32-bit kernel where these are defined in a meaningful way.
[hverkuil: fix 3 warnings: switch with no cases]
Fixes: 577c89b0ce72 ("media: v4l2-core: fix v4l2_buffer handling for time64 ABI") Reported-by: syzbot+142888ffec98ab194028@syzkaller.appspotmail.com Signed-off-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl Signed-off-by: Mauro Carvalho Chehab mchehab+huawei@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/v4l2-core/v4l2-ioctl.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c index 2673f51aafa4..07d823656ee6 100644 --- a/drivers/media/v4l2-core/v4l2-ioctl.c +++ b/drivers/media/v4l2-core/v4l2-ioctl.c @@ -3072,8 +3072,8 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
static unsigned int video_translate_cmd(unsigned int cmd) { +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) switch (cmd) { -#ifdef CONFIG_COMPAT_32BIT_TIME case VIDIOC_DQEVENT_TIME32: return VIDIOC_DQEVENT; case VIDIOC_QUERYBUF_TIME32: @@ -3084,8 +3084,8 @@ static unsigned int video_translate_cmd(unsigned int cmd) return VIDIOC_DQBUF; case VIDIOC_PREPARE_BUF_TIME32: return VIDIOC_PREPARE_BUF; -#endif } +#endif if (in_compat_syscall()) return v4l2_compat_translate_cmd(cmd);
@@ -3126,8 +3126,8 @@ static int video_get_user(void __user *arg, void *parg, } else if (in_compat_syscall()) { err = v4l2_compat_get_user(arg, parg, cmd); } else { +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) switch (cmd) { -#ifdef CONFIG_COMPAT_32BIT_TIME case VIDIOC_QUERYBUF_TIME32: case VIDIOC_QBUF_TIME32: case VIDIOC_DQBUF_TIME32: @@ -3155,8 +3155,8 @@ static int video_get_user(void __user *arg, void *parg, }; break; } -#endif } +#endif }
/* zero out anything we don't copy from userspace */ @@ -3181,8 +3181,8 @@ static int video_put_user(void __user *arg, void *parg, if (in_compat_syscall()) return v4l2_compat_put_user(arg, parg, cmd);
+#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) switch (cmd) { -#ifdef CONFIG_COMPAT_32BIT_TIME case VIDIOC_DQEVENT_TIME32: { struct v4l2_event *ev = parg; struct v4l2_event_time32 ev32; @@ -3230,8 +3230,8 @@ static int video_put_user(void __user *arg, void *parg, return -EFAULT; break; } -#endif } +#endif
return 0; }