[PATCH 0/2] EDAC: Fix sysfs dimm_label show & store operations

[PATCH 0/2] EDAC: Fix sysfs dimm_label show & store operations

[Toshi Kani]

This patch-set fixes the show and store operations of EDAC sysfs
files, "dimm_label" and "chX_dimm_label".

---
Toshi Kani (2):
 1/2 EDAC: Fix sysfs dimm_label show operation
 2/2 EDAC: Fix sysfs dimm_label store operation

---
 drivers/edac/edac_mc_sysfs.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

[PATCH 1/2] EDAC: Fix sysfs dimm_label show operation

[Toshi Kani]

After 'commit 7d375bffa524 ("sb_edac: Fix support for systems with
two home agents per socket")', sysfs "dimm_label" and "chX_dimm_label"
show their label string without a newline "\n" at the end.

 [root@orange ~]# cat /sys/bus/mc0/devices/dimm0/dimm_label
 CPU_SrcID#0_Ha#0_Chan#0_DIMM#0[root@orange ~]#

 [root@orange ~]# cat /sys/devices/system/edac/mc/mc0/csrow0/ch0_dimm_label
 CPU_SrcID#0_Ha#0_Chan#0_DIMM#0[root@orange ~]#

The label strings now have 31 characters, which are the same as
EDAC_MC_LABEL_LEN.  Since the snprintf()s in channel_dimm_label_show()
and dimmdev_label_show() limit the whole length by EDAC_MC_LABEL_LEN,
the newline in the format "%s\n" is ignored.

 [root@orange ~]# od -bc /sys/bus/mc0/devices/dimm0/dimm_label
 0000000 103 120 125 137 123 162 143 111 104 043 060 137 110 141 043 060
           C   P   U   _   S   r   c   I   D   #   0   _   H   a   #   0
 0000020 137 103 150 141 156 043 060 137 104 111 115 115 043 060 000
           _   C   h   a   n   #   0   _   D   I   M   M   #   0  \0
 0000037

Fix it by using 'sizeof(dimm->label) + 1' as the whole length in
the snprintf()s in channel_dimm_label_show() and dimmdev_label_show().

Reported-by: Robert Elliott <elliott@hpe.com>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
---
 drivers/edac/edac_mc_sysfs.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 33df7d9..8983755 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -229,7 +229,7 @@ static ssize_t channel_dimm_label_show(struct device *dev,
 	if (!rank->dimm->label[0])
 		return 0;
 
-	return snprintf(data, EDAC_MC_LABEL_LEN, "%s\n",
+	return snprintf(data, sizeof(rank->dimm->label) + 1, "%s\n",
 			rank->dimm->label);
 }
 
@@ -485,7 +485,7 @@ static ssize_t dimmdev_label_show(struct device *dev,
 	if (!dimm->label[0])
 		return 0;
 
-	return snprintf(data, EDAC_MC_LABEL_LEN, "%s\n", dimm->label);
+	return snprintf(data, sizeof(dimm->label) + 1, "%s\n", dimm->label);
 }
 
 static ssize_t dimmdev_label_store(struct device *dev,

[PATCH 2/2] EDAC: Fix sysfs dimm_label store operation

[Toshi Kani]

Sysfs "dimm_label" and "chX_dimm_label" have the following issues
in their store operation.

 1) A newline-terminated input string causes redundant newlines

  # echo "test" > /sys/bus/mc0/devices/dimm0/dimm_label
  # cat  /sys/bus/mc0/devices/dimm0/dimm_label
  test

  #  od -bc /sys/bus/mc0/devices/dimm0/dimm_label
  0000000 164 145 163 164 012 012
            t   e   s   t  \n  \n
  0000006

 2) The original label string (31 characters) cannot be stored due to
    an improper size check

  # echo "CPU_SrcID#0_Ha#0_Chan#0_DIMM#0" \
  > /sys/bus/mc0/devices/dimm0/dimm_label
  # cat /sys/bus/mc0/devices/dimm0/dimm_label


  # od -bc /sys/bus/mc0/devices/dimm0/dimm_label
   0000000 012 012
            \n  \n
   0000002

 3) An input string longer than the buffer size results a wrong label
    info as it allows a retry with the remaining string.

  # echo "CPU_SrcID#0_Ha#0_Chan#0_DIMM#0_TEST" \
  > /sys/bus/mc0/devices/dimm0/dimm_label
  # cat  /sys/bus/mc0/devices/dimm0/dimm_label
  _TEST

Fix these issues by making the following changes:
 1) Replace a newline character at the end with a null, if any.
 2) Check the label buffer size with 'sizeof(dimm->label)'.
 3) Fail a request if its string exceeds the label buffer size.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: Robert Elliott <elliott@hpe.com>
---
 drivers/edac/edac_mc_sysfs.c |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 8983755..f2ea914 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -241,13 +241,14 @@ static ssize_t channel_dimm_label_store(struct device *dev,
 	unsigned chan = to_channel(mattr);
 	struct rank_info *rank = csrow->channels[chan];
 
-	ssize_t max_size = 0;
+	if (count == 0 || count > sizeof(rank->dimm->label))
+		return -EINVAL;
 
-	max_size = min((ssize_t) count, (ssize_t) EDAC_MC_LABEL_LEN - 1);
-	strncpy(rank->dimm->label, data, max_size);
-	rank->dimm->label[max_size] = '\0';
+	strncpy(rank->dimm->label, data, count);
+	if (rank->dimm->label[count - 1] == '\n')
+		rank->dimm->label[count - 1] = '\0';
 
-	return max_size;
+	return count;
 }
 
 /* show function for dynamic chX_ce_count attribute */
@@ -495,13 +496,14 @@ static ssize_t dimmdev_label_store(struct device *dev,
 {
 	struct dimm_info *dimm = to_dimm(dev);
 
-	ssize_t max_size = 0;
+	if (count == 0 || count > sizeof(dimm->label))
+		return -EINVAL;
 
-	max_size = min((ssize_t) count, (ssize_t) EDAC_MC_LABEL_LEN - 1);
-	strncpy(dimm->label, data, max_size);
-	dimm->label[max_size] = '\0';
+	strncpy(dimm->label, data, count);
+	if (dimm->label[count - 1] == '\n')
+		dimm->label[count - 1] = '\0';
 
-	return max_size;
+	return count;
 }
 
 static ssize_t dimmdev_size_show(struct device *dev,

Re: [PATCH 2/2] EDAC: Fix sysfs dimm_label store operation

[Toshi Kani]

On Mon, 2015-09-21 at 13:19 -0600, Toshi Kani wrote:
 :
> 
> diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
> index 8983755..f2ea914 100644
> --- a/drivers/edac/edac_mc_sysfs.c
> +++ b/drivers/edac/edac_mc_sysfs.c
> @@ -241,13 +241,14 @@ static ssize_t channel_dimm_label_store(struct
> device *dev,
>  	unsigned chan = to_channel(mattr);
>  	struct rank_info *rank = csrow->channels[chan];
>  
> -	ssize_t max_size = 0;
> +	if (count == 0 || count > sizeof(rank->dimm->label))
> +		return -EINVAL;
>  
> -	max_size = min((ssize_t) count, (ssize_t) EDAC_MC_LABEL_LEN - 1);
> -	strncpy(rank->dimm->label, data, max_size);
> -	rank->dimm->label[max_size] = '\0';
> +	strncpy(rank->dimm->label, data, count);
> +	if (rank->dimm->label[count - 1] == '\n')
> +		rank->dimm->label[count - 1] = '\0';

Thinking further, it'd be safer to always set a null at the end.  I will
update the patch.

-Toshi

RE: [PATCH 0/2] EDAC: Fix sysfs dimm_label show & store operations

[Luck, Tony]

Toshi Kani (2):
 1/2 EDAC: Fix sysfs dimm_label show operation
 2/2 EDAC: Fix sysfs dimm_label store operation

Looks good.  Both parts:

Acked-by: Tony Luck <tony.luck@intel.com>