[alsa-devel] [PATCH v2 4/8] ASoC: imx-audmux: change snprintf to scnprintf for possible overflow
From: Silvio Cesare silvio.cesare@gmail.com
Change snprintf to scnprintf. There are generally two cases where using snprintf causes problems.
1) Uses of size += snprintf(buf, SIZE - size, fmt, ...) In this case, if snprintf would have written more characters than what the buffer size (SIZE) is, then size will end up larger than SIZE. In later uses of snprintf, SIZE - size will result in a negative number, leading to problems. Note that size might already be too large by using size = snprintf before the code reaches a case of size += snprintf.
2) If size is ultimately used as a length parameter for a copy back to user space, then it will potentially allow for a buffer overflow and information disclosure when size is greater than SIZE. When the size is used to index the buffer directly, we can have memory corruption. This also means when size = snprintf... is used, it may also cause problems since size may become large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel configuration.
The solution to these issues is to use scnprintf which returns the number of characters actually written to the buffer, so the size variable will never exceed SIZE.
Signed-off-by: Silvio Cesare silvio.cesare@gmail.com Cc: Timur Tabi timur@kernel.org Cc: Nicolin Chen nicoleotsuka@gmail.com Cc: Mark Brown broonie@kernel.org Cc: Xiubo Li Xiubo.Lee@gmail.com Cc: Fabio Estevam fabio.estevam@nxp.com Cc: Dan Carpenter dan.carpenter@oracle.com Cc: Kees Cook keescook@chromium.org Cc: Will Deacon will.deacon@arm.com Cc: Greg KH greg@kroah.com Signed-off-by: Willy Tarreau w@1wt.eu Acked-by: Nicolin Chen nicoleotsuka@gmail.com Reviewed-by: Kees Cook keescook@chromium.org
--
v2: - adjust subject line - added alsa-devel & Mark - added acked-by - added reviewed-by
The patches in this series were sent by Silvio to the security list to fix a minor memory disclosure issue after this article was published:
http://blog.infosectcbr.com.au/2018/11/memory-bugs-in-multiple-linux-kernel....
sound/soc/fsl/imx-audmux.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/sound/soc/fsl/imx-audmux.c b/sound/soc/fsl/imx-audmux.c index 392d5eef356d..99e07b01a2ce 100644 --- a/sound/soc/fsl/imx-audmux.c +++ b/sound/soc/fsl/imx-audmux.c @@ -86,49 +86,49 @@ static ssize_t audmux_read_file(struct file *file, char __user *user_buf, if (!buf) return -ENOMEM;
- ret = snprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n", + ret = scnprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n", pdcr, ptcr);
if (ptcr & IMX_AUDMUX_V2_PTCR_TFSDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS output from %s, ", audmux_port_string((ptcr >> 27) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS input, ");
if (ptcr & IMX_AUDMUX_V2_PTCR_TCLKDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk output from %s", audmux_port_string((ptcr >> 22) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk input");
- ret += snprintf(buf + ret, PAGE_SIZE - ret, "\n"); + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
if (ptcr & IMX_AUDMUX_V2_PTCR_SYN) { - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "Port is symmetric"); } else { if (ptcr & IMX_AUDMUX_V2_PTCR_RFSDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS output from %s, ", audmux_port_string((ptcr >> 17) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS input, ");
if (ptcr & IMX_AUDMUX_V2_PTCR_RCLKDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk output from %s", audmux_port_string((ptcr >> 12) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk input"); }
- ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\nData received from %s\n", audmux_port_string((pdcr >> 13) & 0x7));
Hi Willy,
On 1/14/19 9:27 PM, Willy Tarreau wrote:
From: Silvio Cesare silvio.cesare@gmail.com
Change snprintf to scnprintf. There are generally two cases where using snprintf causes problems.
- Uses of size += snprintf(buf, SIZE - size, fmt, ...)
In this case, if snprintf would have written more characters than what the buffer size (SIZE) is, then size will end up larger than SIZE. In later uses of snprintf, SIZE - size will result in a negative number, leading to problems. Note that size might already be too large by using size = snprintf before the code reaches a case of size += snprintf.
- If size is ultimately used as a length parameter for a copy back to user
space, then it will potentially allow for a buffer overflow and information disclosure when size is greater than SIZE. When the size is used to index the buffer directly, we can have memory corruption. This also means when size = snprintf... is used, it may also cause problems since size may become large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel configuration.
The solution to these issues is to use scnprintf which returns the number of characters actually written to the buffer, so the size variable will never exceed SIZE.
Signed-off-by: Silvio Cesare silvio.cesare@gmail.com Cc: Timur Tabi timur@kernel.org Cc: Nicolin Chen nicoleotsuka@gmail.com Cc: Mark Brown broonie@kernel.org Cc: Xiubo Li Xiubo.Lee@gmail.com Cc: Fabio Estevam fabio.estevam@nxp.com Cc: Dan Carpenter dan.carpenter@oracle.com Cc: Kees Cook keescook@chromium.org Cc: Will Deacon will.deacon@arm.com Cc: Greg KH greg@kroah.com Signed-off-by: Willy Tarreau w@1wt.eu Acked-by: Nicolin Chen nicoleotsuka@gmail.com Reviewed-by: Kees Cook keescook@chromium.org
You are still missing some people and mailing lists:
$ scripts/get_maintainer.pl --nokeywords --nogit --nogit-fallback sound/soc/fsl/imx-audmux.c Timur Tabi timur@kernel.org (maintainer:FREESCALE SOC SOUND DRIVERS) Nicolin Chen nicoleotsuka@gmail.com (maintainer:FREESCALE SOC SOUND DRIVERS) Xiubo Li Xiubo.Lee@gmail.com (maintainer:FREESCALE SOC SOUND DRIVERS) Fabio Estevam fabio.estevam@nxp.com (reviewer:FREESCALE SOC SOUND DRIVERS) Liam Girdwood lgirdwood@gmail.com (supporter:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM...) Mark Brown broonie@kernel.org (supporter:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM...) Jaroslav Kysela perex@perex.cz (maintainer:SOUND) Takashi Iwai tiwai@suse.com (maintainer:SOUND) Shawn Guo shawnguo@kernel.org (maintainer:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) Sascha Hauer s.hauer@pengutronix.de (maintainer:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) Pengutronix Kernel Team kernel@pengutronix.de (reviewer:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) NXP Linux Team linux-imx@nxp.com (reviewer:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) alsa-devel@alsa-project.org (moderated list:FREESCALE SOC SOUND DRIVERS) linuxppc-dev@lists.ozlabs.org (open list:FREESCALE SOC SOUND DRIVERS) linux-arm-kernel@lists.infradead.org (moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE) linux-kernel@vger.kernel.org (open list)
-- Gustavo
--
v2:
- adjust subject line
- added alsa-devel & Mark
- added acked-by
- added reviewed-by
The patches in this series were sent by Silvio to the security list to fix a minor memory disclosure issue after this article was published:
http://blog.infosectcbr.com.au/2018/11/memory-bugs-in-multiple-linux-kernel....
sound/soc/fsl/imx-audmux.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/sound/soc/fsl/imx-audmux.c b/sound/soc/fsl/imx-audmux.c index 392d5eef356d..99e07b01a2ce 100644 --- a/sound/soc/fsl/imx-audmux.c +++ b/sound/soc/fsl/imx-audmux.c @@ -86,49 +86,49 @@ static ssize_t audmux_read_file(struct file *file, char __user *user_buf, if (!buf) return -ENOMEM;
- ret = snprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n",
ret = scnprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n", pdcr, ptcr);
if (ptcr & IMX_AUDMUX_V2_PTCR_TFSDIR)
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS output from %s, ", audmux_port_string((ptcr >> 27) & 0x7));
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS input, ");if (ptcr & IMX_AUDMUX_V2_PTCR_TCLKDIR)
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk output from %s", audmux_port_string((ptcr >> 22) & 0x7));
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk input");
- ret += snprintf(buf + ret, PAGE_SIZE - ret, "\n");
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
if (ptcr & IMX_AUDMUX_V2_PTCR_SYN) {
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "Port is symmetric");
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS output from %s, ", audmux_port_string((ptcr >> 17) & 0x7));
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS input, ");if (ptcr & IMX_AUDMUX_V2_PTCR_RCLKDIR)
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk output from %s", audmux_port_string((ptcr >> 12) & 0x7));
ret += snprintf(buf + ret, PAGE_SIZE - ret,
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk input");
- ret += snprintf(buf + ret, PAGE_SIZE - ret,
- ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\nData received from %s\n", audmux_port_string((pdcr >> 13) & 0x7));
The patch
ASoC: imx-audmux: change snprintf to scnprintf for possible overflow
has been applied to the asoc tree at
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git
All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.
You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.
If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.
Please add any relevant lists and maintainers to the CCs when replying to this mail.
Thanks, Mark
From c407cd008fd039320d147088b52d0fa34ed3ddcb Mon Sep 17 00:00:00 2001
From: Silvio Cesare silvio.cesare@gmail.com Date: Tue, 15 Jan 2019 04:27:27 +0100 Subject: [PATCH] ASoC: imx-audmux: change snprintf to scnprintf for possible overflow
Change snprintf to scnprintf. There are generally two cases where using snprintf causes problems.
1) Uses of size += snprintf(buf, SIZE - size, fmt, ...) In this case, if snprintf would have written more characters than what the buffer size (SIZE) is, then size will end up larger than SIZE. In later uses of snprintf, SIZE - size will result in a negative number, leading to problems. Note that size might already be too large by using size = snprintf before the code reaches a case of size += snprintf.
2) If size is ultimately used as a length parameter for a copy back to user space, then it will potentially allow for a buffer overflow and information disclosure when size is greater than SIZE. When the size is used to index the buffer directly, we can have memory corruption. This also means when size = snprintf... is used, it may also cause problems since size may become large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel configuration.
The solution to these issues is to use scnprintf which returns the number of characters actually written to the buffer, so the size variable will never exceed SIZE.
Signed-off-by: Silvio Cesare silvio.cesare@gmail.com Cc: Timur Tabi timur@kernel.org Cc: Nicolin Chen nicoleotsuka@gmail.com Cc: Mark Brown broonie@kernel.org Cc: Xiubo Li Xiubo.Lee@gmail.com Cc: Fabio Estevam fabio.estevam@nxp.com Cc: Dan Carpenter dan.carpenter@oracle.com Cc: Kees Cook keescook@chromium.org Cc: Will Deacon will.deacon@arm.com Cc: Greg KH greg@kroah.com Signed-off-by: Willy Tarreau w@1wt.eu Acked-by: Nicolin Chen nicoleotsuka@gmail.com Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: Mark Brown broonie@kernel.org --- sound/soc/fsl/imx-audmux.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/sound/soc/fsl/imx-audmux.c b/sound/soc/fsl/imx-audmux.c index 392d5eef356d..99e07b01a2ce 100644 --- a/sound/soc/fsl/imx-audmux.c +++ b/sound/soc/fsl/imx-audmux.c @@ -86,49 +86,49 @@ static ssize_t audmux_read_file(struct file *file, char __user *user_buf, if (!buf) return -ENOMEM;
- ret = snprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n", + ret = scnprintf(buf, PAGE_SIZE, "PDCR: %08x\nPTCR: %08x\n", pdcr, ptcr);
if (ptcr & IMX_AUDMUX_V2_PTCR_TFSDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS output from %s, ", audmux_port_string((ptcr >> 27) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxFS input, ");
if (ptcr & IMX_AUDMUX_V2_PTCR_TCLKDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk output from %s", audmux_port_string((ptcr >> 22) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "TxClk input");
- ret += snprintf(buf + ret, PAGE_SIZE - ret, "\n"); + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
if (ptcr & IMX_AUDMUX_V2_PTCR_SYN) { - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "Port is symmetric"); } else { if (ptcr & IMX_AUDMUX_V2_PTCR_RFSDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS output from %s, ", audmux_port_string((ptcr >> 17) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxFS input, ");
if (ptcr & IMX_AUDMUX_V2_PTCR_RCLKDIR) - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk output from %s", audmux_port_string((ptcr >> 12) & 0x7)); else - ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "RxClk input"); }
- ret += snprintf(buf + ret, PAGE_SIZE - ret, + ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\nData received from %s\n", audmux_port_string((pdcr >> 13) & 0x7));
participants (3)
-
Gustavo A. R. Silva -
Mark Brown -
Willy Tarreau