* Re: [PATCH] firmware: xilinx: fix debugfs write handler
2019-02-18 21:43 [PATCH] firmware: xilinx: fix debugfs write handler Jann Horn
@ 2019-02-28 13:59 ` Michal Simek
2019-03-05 18:57 ` Jolly Shah
2019-03-18 12:44 ` Michal Simek
2 siblings, 0 replies; 4+ messages in thread
From: Michal Simek @ 2019-02-28 13:59 UTC (permalink / raw)
To: Jann Horn, Michal Simek
Cc: Rajan Vaja, Jolly Shah, linux-arm-kernel, linux-kernel
On 18. 02. 19 22:43, Jann Horn wrote:
> - Userspace wants to write a string with `len` bytes, not counting the
> terminating NULL, so we should allocate `len+1` bytes. It looks like the
> current code relied on having a nullbyte directly behind `kern_buff`,
> which happens to work reliably as long as `len` isn't one of the kmalloc
> size classes.
> - strncpy_from_user() is completely wrong here; userspace is giving us a
> (not necessarily null-terminated) buffer and its length.
> strncpy_from_user() is for cases in which we don't know the length.
> - Don't let broken userspace allocate arbitrarily big kmalloc allocations.
>
> Just use memdup_user_nul(), which is designed precisely for things like
> this.
>
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
> WARNING: completely untested patch
>
> drivers/firmware/xilinx/zynqmp-debug.c | 15 ++++-----------
> 1 file changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/firmware/xilinx/zynqmp-debug.c b/drivers/firmware/xilinx/zynqmp-debug.c
> index 2771df6df379..90b66cdbfd58 100644
> --- a/drivers/firmware/xilinx/zynqmp-debug.c
> +++ b/drivers/firmware/xilinx/zynqmp-debug.c
> @@ -163,21 +163,14 @@ static ssize_t zynqmp_pm_debugfs_api_write(struct file *file,
>
> strcpy(debugfs_buf, "");
>
> - if (*off != 0 || len == 0)
> + if (*off != 0 || len <= 1 || len > PAGE_SIZE - 1)
> return -EINVAL;
>
> - kern_buff = kzalloc(len, GFP_KERNEL);
> - if (!kern_buff)
> - return -ENOMEM;
> -
> + kern_buff = memdup_user_nul(ptr, len);
> + if (IS_ERR(kern_buff))
> + return PTR_ERR(kern_buff);
> tmp_buff = kern_buff;
>
> - ret = strncpy_from_user(kern_buff, ptr, len);
> - if (ret < 0) {
> - ret = -EFAULT;
> - goto err;
> - }
> -
> /* Read the API name from a user request */
> pm_api_req = strsep(&kern_buff, " ");
>
>
Jolly: Can you please retest it and ACK?
Thanks,
Michal
^ permalink raw reply [flat|nested] 4+ messages in thread* RE: [PATCH] firmware: xilinx: fix debugfs write handler
2019-02-18 21:43 [PATCH] firmware: xilinx: fix debugfs write handler Jann Horn
2019-02-28 13:59 ` Michal Simek
@ 2019-03-05 18:57 ` Jolly Shah
2019-03-18 12:44 ` Michal Simek
2 siblings, 0 replies; 4+ messages in thread
From: Jolly Shah @ 2019-03-05 18:57 UTC (permalink / raw)
To: Jann Horn, Michal Simek; +Cc: Rajan Vaja, linux-arm-kernel, linux-kernel
Acked-by: Jolly Shah <jollys@xilinx.com>
> -----Original Message-----
> From: Jann Horn <jannh@google.com>
> Sent: Monday, February 18, 2019 1:43 PM
> To: Michal Simek <michals@xilinx.com>; jannh@google.com
> Cc: Rajan Vaja <RAJANV@xilinx.com>; Jolly Shah <JOLLYS@xilinx.com>; linux-
> arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: [PATCH] firmware: xilinx: fix debugfs write handler
>
> - Userspace wants to write a string with `len` bytes, not counting the
> terminating NULL, so we should allocate `len+1` bytes. It looks like the
> current code relied on having a nullbyte directly behind `kern_buff`,
> which happens to work reliably as long as `len` isn't one of the kmalloc
> size classes.
> - strncpy_from_user() is completely wrong here; userspace is giving us a
> (not necessarily null-terminated) buffer and its length.
> strncpy_from_user() is for cases in which we don't know the length.
> - Don't let broken userspace allocate arbitrarily big kmalloc allocations.
>
> Just use memdup_user_nul(), which is designed precisely for things like
> this.
>
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
> WARNING: completely untested patch
>
> drivers/firmware/xilinx/zynqmp-debug.c | 15 ++++-----------
> 1 file changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/firmware/xilinx/zynqmp-debug.c
> b/drivers/firmware/xilinx/zynqmp-debug.c
> index 2771df6df379..90b66cdbfd58 100644
> --- a/drivers/firmware/xilinx/zynqmp-debug.c
> +++ b/drivers/firmware/xilinx/zynqmp-debug.c
> @@ -163,21 +163,14 @@ static ssize_t zynqmp_pm_debugfs_api_write(struct
> file *file,
>
> strcpy(debugfs_buf, "");
>
> - if (*off != 0 || len == 0)
> + if (*off != 0 || len <= 1 || len > PAGE_SIZE - 1)
> return -EINVAL;
>
> - kern_buff = kzalloc(len, GFP_KERNEL);
> - if (!kern_buff)
> - return -ENOMEM;
> -
> + kern_buff = memdup_user_nul(ptr, len);
> + if (IS_ERR(kern_buff))
> + return PTR_ERR(kern_buff);
> tmp_buff = kern_buff;
>
> - ret = strncpy_from_user(kern_buff, ptr, len);
> - if (ret < 0) {
> - ret = -EFAULT;
> - goto err;
> - }
> -
> /* Read the API name from a user request */
> pm_api_req = strsep(&kern_buff, " ");
>
> --
> 2.21.0.rc0.258.g878e2cd30e-goog
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] firmware: xilinx: fix debugfs write handler
2019-02-18 21:43 [PATCH] firmware: xilinx: fix debugfs write handler Jann Horn
2019-02-28 13:59 ` Michal Simek
2019-03-05 18:57 ` Jolly Shah
@ 2019-03-18 12:44 ` Michal Simek
2 siblings, 0 replies; 4+ messages in thread
From: Michal Simek @ 2019-03-18 12:44 UTC (permalink / raw)
To: Jann Horn, Michal Simek
Cc: Rajan Vaja, Jolly Shah, linux-arm-kernel, linux-kernel
On 18. 02. 19 22:43, Jann Horn wrote:
> - Userspace wants to write a string with `len` bytes, not counting the
> terminating NULL, so we should allocate `len+1` bytes. It looks like the
> current code relied on having a nullbyte directly behind `kern_buff`,
> which happens to work reliably as long as `len` isn't one of the kmalloc
> size classes.
> - strncpy_from_user() is completely wrong here; userspace is giving us a
> (not necessarily null-terminated) buffer and its length.
> strncpy_from_user() is for cases in which we don't know the length.
> - Don't let broken userspace allocate arbitrarily big kmalloc allocations.
>
> Just use memdup_user_nul(), which is designed precisely for things like
> this.
>
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
> WARNING: completely untested patch
>
> drivers/firmware/xilinx/zynqmp-debug.c | 15 ++++-----------
> 1 file changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/firmware/xilinx/zynqmp-debug.c b/drivers/firmware/xilinx/zynqmp-debug.c
> index 2771df6df379..90b66cdbfd58 100644
> --- a/drivers/firmware/xilinx/zynqmp-debug.c
> +++ b/drivers/firmware/xilinx/zynqmp-debug.c
> @@ -163,21 +163,14 @@ static ssize_t zynqmp_pm_debugfs_api_write(struct file *file,
>
> strcpy(debugfs_buf, "");
>
> - if (*off != 0 || len == 0)
> + if (*off != 0 || len <= 1 || len > PAGE_SIZE - 1)
> return -EINVAL;
>
> - kern_buff = kzalloc(len, GFP_KERNEL);
> - if (!kern_buff)
> - return -ENOMEM;
> -
> + kern_buff = memdup_user_nul(ptr, len);
> + if (IS_ERR(kern_buff))
> + return PTR_ERR(kern_buff);
> tmp_buff = kern_buff;
>
> - ret = strncpy_from_user(kern_buff, ptr, len);
> - if (ret < 0) {
> - ret = -EFAULT;
> - goto err;
> - }
> -
> /* Read the API name from a user request */
> pm_api_req = strsep(&kern_buff, " ");
>
>
applied with Jolly's ack.
Thanks,
Michal
^ permalink raw reply [flat|nested] 4+ messages in thread