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 Reported-by: Christian Kujau <li...@nerdbynature.de> CC: sta...@vger.kernel.org Signed-off-by: Josh Boyer <jwbo...@redhat.com> --- kernel/printk.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/printk.c b/kernel/printk.c index f24633a..398ef9a 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -615,6 +615,9 @@ static int devkmsg_open(struct inode *inode, struct file *file) 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; -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
