On 13.11.2019 18.00, Jann Horn wrote:
On Wed, Nov 13, 2019 at 12:22 AM Christian Brauner
<christian.brauner@xxxxxxxxxx> wrote:
On Sun, Nov 03, 2019 at 04:55:48PM +0200, Topi Miettinen wrote:
Several items in /proc/sys need not be accessible to unprivileged
tasks. Let the system administrator change the permissions, but only
to more restrictive modes than what the sysctl tables allow.
Signed-off-by: Topi Miettinen <toiwoton@xxxxxxxxx>
---
fs/proc/proc_sysctl.c | 41 +++++++++++++++++++++++++++++++----------
1 file changed, 31 insertions(+), 10 deletions(-)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index d80989b6c344..88c4ca7d2782 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -818,6 +818,10 @@ static int proc_sys_permission(struct inode *inode, int
mask)
if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
return -EACCES;
+ error = generic_permission(inode, mask);
+ if (error)
+ return error;
In kernel/ucount.c, the ->permissions handler set_permissions() grants
access based on whether the caller has CAP_SYS_RESOURCE. And in
net/sysctl_net.c, the handler net_ctl_permissions() grants access
based on whether the caller has CAP_NET_ADMIN. This added check is
going to break those, right?
Right. The comment above seems then a bit misleading:
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
-Topi
