From 078da2408e2e65f4ff5d115df71775dde02161bf Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Tue, 9 Apr 2013 13:27:49 -0400 Subject: [PATCH] Update dmesg_restrict patch to v2 --- ...or-dmesg_restrict-sysctl-on-dev-kmsg.patch | 166 +++++++++++++++--- 1 file changed, 141 insertions(+), 25 deletions(-) diff --git a/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch b/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch index acaf5f881..c42c8c4f1 100644 --- a/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch +++ b/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch @@ -1,46 +1,162 @@ -From feaf4959c30d0640093a607c577940d3e9351076 Mon Sep 17 00:00:00 2001 +From ce10d1b72b4da3c98bbbcb1b945687d964c31923 Mon Sep 17 00:00:00 2001 From: Josh Boyer -Date: Fri, 22 Feb 2013 11:47:37 -0500 +Date: Tue, 9 Apr 2013 11:08:13 -0400 Subject: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg -Originally, the addition of the 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. +The dmesg_restrict sysctl currently covers the syslog method for access +dmesg, however /dev/kmsg isn't covered by the same protections. Most +people haven't noticed because util-linux dmesg(1) defaults to using the +syslog method for access in older versions. With util-linux dmesg(1) +defaults to reading directly from /dev/kmsg. -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. +Fix this by reworking all of the access methods to use the +check_syslog_permissions function and adding checks to devkmsg_open and +devkmsg_read. This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192 Reported-by: Christian Kujau CC: stable@vger.kernel.org +Signed-off-by: Eric Paris Signed-off-by: Josh Boyer --- - kernel/printk.c | 3 +++ - 1 file changed, 3 insertions(+) + kernel/printk.c | 91 +++++++++++++++++++++++++++++---------------------------- + 1 file changed, 47 insertions(+), 44 deletions(-) diff --git a/kernel/printk.c b/kernel/printk.c -index f24633a..398ef9a 100644 +index abbdd9e..5541095 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; +@@ -368,6 +368,46 @@ static void log_store(int facility, int level, + log_next_seq++; + } -+ if (dmesg_restrict && !capable(CAP_SYSLOG)) -+ return -EACCES; ++#ifdef CONFIG_SECURITY_DMESG_RESTRICT ++int dmesg_restrict = 1; ++#else ++int dmesg_restrict; ++#endif + - /* write-only does not need any file context */ ++static int syslog_action_restricted(int type) ++{ ++ if (dmesg_restrict) ++ return 1; ++ /* Unless restricted, we allow "read all" and "get buffer size" for everybody */ ++ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER; ++} ++ ++static int check_syslog_permissions(int type, bool from_file) ++{ ++ /* ++ * If this is from /proc/kmsg and we've already opened it, then we've ++ * already done the capabilities checks at open time. ++ */ ++ if (from_file && type != SYSLOG_ACTION_OPEN) ++ goto ok; ++ ++ if (syslog_action_restricted(type)) { ++ if (capable(CAP_SYSLOG)) ++ goto ok; ++ /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ ++ if (capable(CAP_SYS_ADMIN)) { ++ printk_once(KERN_WARNING "%s (%d): " ++ "Attempt to access syslog with CAP_SYS_ADMIN " ++ "but no CAP_SYSLOG (deprecated).\n", ++ current->comm, task_pid_nr(current)); ++ goto ok; ++ } ++ return -EPERM; ++ } ++ok: ++ return security_syslog(type); ++} ++ + /* /dev/kmsg - userspace message inject/listen interface */ + struct devkmsg_user { + u64 seq; +@@ -443,10 +483,16 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, + char cont = '-'; + size_t len; + ssize_t ret; ++ int err; + + if (!user) + return -EBADF; + ++ err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, ++ SYSLOG_FROM_FILE); ++ if (err) ++ return err; ++ + ret = mutex_lock_interruptible(&user->lock); + if (ret) + return ret; +@@ -624,7 +670,7 @@ static int devkmsg_open(struct inode *inode, struct file *file) if ((file->f_flags & O_ACCMODE) == O_WRONLY) return 0; + +- err = security_syslog(SYSLOG_ACTION_READ_ALL); ++ err = check_syslog_permissions(SYSLOG_ACTION_OPEN, SYSLOG_FROM_FILE); + if (err) + return err; + +@@ -817,45 +863,6 @@ static inline void boot_delay_msec(int level) + } + #endif + +-#ifdef CONFIG_SECURITY_DMESG_RESTRICT +-int dmesg_restrict = 1; +-#else +-int dmesg_restrict; +-#endif +- +-static int syslog_action_restricted(int type) +-{ +- if (dmesg_restrict) +- return 1; +- /* Unless restricted, we allow "read all" and "get buffer size" for everybody */ +- return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER; +-} +- +-static int check_syslog_permissions(int type, bool from_file) +-{ +- /* +- * If this is from /proc/kmsg and we've already opened it, then we've +- * already done the capabilities checks at open time. +- */ +- if (from_file && type != SYSLOG_ACTION_OPEN) +- return 0; +- +- if (syslog_action_restricted(type)) { +- if (capable(CAP_SYSLOG)) +- return 0; +- /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ +- if (capable(CAP_SYS_ADMIN)) { +- printk_once(KERN_WARNING "%s (%d): " +- "Attempt to access syslog with CAP_SYS_ADMIN " +- "but no CAP_SYSLOG (deprecated).\n", +- current->comm, task_pid_nr(current)); +- return 0; +- } +- return -EPERM; +- } +- return 0; +-} +- + #if defined(CONFIG_PRINTK_TIME) + static bool printk_time = 1; + #else +@@ -1131,10 +1138,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file) + if (error) + goto out; + +- error = security_syslog(type); +- if (error) +- return error; +- + switch (type) { + case SYSLOG_ACTION_CLOSE: /* Close log */ + break; -- -1.8.1.2 +1.8.1.4