Re: [PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Luis R. Rodriguez]

On Wed, Feb 28, 2018 at 12:31:55AM +0100, Danilo Krummrich wrote:
> proc_sys_link_fill_cache() does not take currently unregistering
> sysctl tables into account, which might result into a page fault in
> sysctl_follow_link() - add a check to fix it.
> 
> Signed-off-by: Danilo Krummrich 
> ---
> v2: removed empty line between between sysctl_head_grab and IS_ERR

Please add a respective tag:

Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between 
sysctl_table_sets")

And mention this has been present since v3.4. May be worth sending to
stable as well, so peg stable as well.

  Luis

> ---
>  fs/proc/proc_sysctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c5cbbdff3c3d..82ac5f682b73 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
>   struct ctl_table *table)
>  {
>   bool ret = true;
> +
>   head = sysctl_head_grab(head);
> + if (IS_ERR(head))
> + return false;
>  
>   if (S_ISLNK(table->mode)) {
>   /* It is not an error if we can not follow the link ignore it */
> -- 
> 2.14.1
> 
> 

-- 
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg

Re: [PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Luis R. Rodriguez]

On Wed, Feb 28, 2018 at 12:31:55AM +0100, Danilo Krummrich wrote:
> proc_sys_link_fill_cache() does not take currently unregistering
> sysctl tables into account, which might result into a page fault in
> sysctl_follow_link() - add a check to fix it.
> 
> Signed-off-by: Danilo Krummrich 
> ---
> v2: removed empty line between between sysctl_head_grab and IS_ERR

Please add a respective tag:

Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between 
sysctl_table_sets")

And mention this has been present since v3.4. May be worth sending to
stable as well, so peg stable as well.

  Luis

> ---
>  fs/proc/proc_sysctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c5cbbdff3c3d..82ac5f682b73 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
>   struct ctl_table *table)
>  {
>   bool ret = true;
> +
>   head = sysctl_head_grab(head);
> + if (IS_ERR(head))
> + return false;
>  
>   if (S_ISLNK(table->mode)) {
>   /* It is not an error if we can not follow the link ignore it */
> -- 
> 2.14.1
> 
> 

-- 
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg

Re: [PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Kees Cook]

On Tue, Feb 27, 2018 at 3:31 PM, Danilo Krummrich
 wrote:
> proc_sys_link_fill_cache() does not take currently unregistering
> sysctl tables into account, which might result into a page fault in
> sysctl_follow_link() - add a check to fix it.
>
> Signed-off-by: Danilo Krummrich 

Acked-by: Kees Cook 

> ---
> v2: removed empty line between between sysctl_head_grab and IS_ERR

Thanks!

-Kees

> ---
>  fs/proc/proc_sysctl.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c5cbbdff3c3d..82ac5f682b73 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
> struct ctl_table *table)
>  {
> bool ret = true;
> +
> head = sysctl_head_grab(head);
> +   if (IS_ERR(head))
> +   return false;
>
> if (S_ISLNK(table->mode)) {
> /* It is not an error if we can not follow the link ignore it 
> */
> --
> 2.14.1
>



-- 
Kees Cook
Pixel Security

Re: [PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Kees Cook]

On Tue, Feb 27, 2018 at 3:31 PM, Danilo Krummrich
 wrote:
> proc_sys_link_fill_cache() does not take currently unregistering
> sysctl tables into account, which might result into a page fault in
> sysctl_follow_link() - add a check to fix it.
>
> Signed-off-by: Danilo Krummrich 

Acked-by: Kees Cook 

> ---
> v2: removed empty line between between sysctl_head_grab and IS_ERR

Thanks!

-Kees

> ---
>  fs/proc/proc_sysctl.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c5cbbdff3c3d..82ac5f682b73 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
> struct ctl_table *table)
>  {
> bool ret = true;
> +
> head = sysctl_head_grab(head);
> +   if (IS_ERR(head))
> +   return false;
>
> if (S_ISLNK(table->mode)) {
> /* It is not an error if we can not follow the link ignore it 
> */
> --
> 2.14.1
>



-- 
Kees Cook
Pixel Security

[PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Danilo Krummrich]

proc_sys_link_fill_cache() does not take currently unregistering
sysctl tables into account, which might result into a page fault in
sysctl_follow_link() - add a check to fix it.

Signed-off-by: Danilo Krummrich 
---
v2: removed empty line between between sysctl_head_grab and IS_ERR
---
 fs/proc/proc_sysctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c5cbbdff3c3d..82ac5f682b73 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
struct ctl_table *table)
 {
bool ret = true;
+
head = sysctl_head_grab(head);
+   if (IS_ERR(head))
+   return false;
 
if (S_ISLNK(table->mode)) {
/* It is not an error if we can not follow the link ignore it */
-- 
2.14.1

[PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Danilo Krummrich]

proc_sys_link_fill_cache() does not take currently unregistering
sysctl tables into account, which might result into a page fault in
sysctl_follow_link() - add a check to fix it.

Signed-off-by: Danilo Krummrich 
---
v2: removed empty line between between sysctl_head_grab and IS_ERR
---
 fs/proc/proc_sysctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c5cbbdff3c3d..82ac5f682b73 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
struct ctl_table *table)
 {
bool ret = true;
+
head = sysctl_head_grab(head);
+   if (IS_ERR(head))
+   return false;
 
if (S_ISLNK(table->mode)) {
/* It is not an error if we can not follow the link ignore it */
-- 
2.14.1