Messages in this thread Patch in this message | | | Date | Fri, 22 Mar 2013 14:54:48 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg |
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poke. Nothing got applied. I'll drop kmsg-honor-dmesg_restrict-sysctl-on-dev-kmsg.patch, see if that has any effect ;)
From: Josh Boyer <jwboyer@redhat.com> Subject: kmsg: honor dmesg_restrict sysctl on /dev/kmsg
Originally, the addition of dmesg_restrict covered both the syslog method of accessing dmesg, as well as /dev/kmsg itself. This was done indirectly by security_syslog calling cap_syslog before doing any LSM checks.
However, commit 12b3052c3ee ("capabilities/syslog: open code cap_syslog logic to fix build failure") moved the code around and pushed the checks into the caller itself. That seems to have inadvertently dropped the checks for dmesg_restrict on /dev/kmsg. Most people haven't noticed because util-linux dmesg(1) defaults to using the syslog method for access in older versions. With util-linux 2.22 and a kernel newer than 3.5, dmesg(1) defaults to reading directly from /dev/kmsg.
Fix this by making an explicit check in the devkmsg_open function.
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192
Signed-off-by: Josh Boyer <jwboyer@redhat.com> Reported-by: Christian Kujau <lists@nerdbynature.de> Cc: Eric Paris <eparis@redhat.com> Cc: James Morris <jmorris@namei.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
kernel/printk.c | 3 +++ 1 file changed, 3 insertions(+)
diff -puN kernel/printk.c~kmsg-honor-dmesg_restrict-sysctl-on-dev-kmsg kernel/printk.c --- a/kernel/printk.c~kmsg-honor-dmesg_restrict-sysctl-on-dev-kmsg +++ a/kernel/printk.c @@ -620,6 +620,9 @@ static int devkmsg_open(struct inode *in struct devkmsg_user *user; int err; + if (dmesg_restrict && !capable(CAP_SYSLOG)) + return -EACCES; + /* write-only does not need any file context */ if ((file->f_flags & O_ACCMODE) == O_WRONLY) return 0; _
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