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 c42c8c4f1..7197f7f7a 100644 --- a/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch +++ b/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch @@ -1,33 +1,106 @@ -From ce10d1b72b4da3c98bbbcb1b945687d964c31923 Mon Sep 17 00:00:00 2001 -From: Josh Boyer -Date: Tue, 9 Apr 2013 11:08:13 -0400 -Subject: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg +To fix /dev/kmsg, let's compare the existing interfaces and what they allow: -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. +- /proc/kmsg allows: + - open (SYSLOG_ACTION_OPEN) if CAP_SYSLOG since it uses a destructive + single-reader interface (SYSLOG_ACTION_READ). + - everything, after an open. -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. +- syslog syscall allows: + - anything, if CAP_SYSLOG. + - SYSLOG_ACTION_READ_ALL and SYSLOG_ACTION_SIZE_BUFFER, if dmesg_restrict==0. + - nothing else (EPERM). -This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192 +The use-cases were: +- dmesg(1) needs to do non-destructive SYSLOG_ACTION_READ_ALLs. +- sysklog(1) needs to open /proc/kmsg, drop privs, and still issue the + destructive SYSLOG_ACTION_READs. +AIUI, dmesg(1) is moving to /dev/kmsg, and systemd-journald doesn't +clear the ring buffer. + +Based on the comments in devkmsg_llseek, it sounds like actions besides +reading aren't going to be supported by /dev/kmsg (i.e. SYSLOG_ACTION_CLEAR), +so we have a strict subset of the non-destructive syslog syscall actions. + +To this end, move the check as Josh had done, but also rename the constants +to reflect their new uses (SYSLOG_FROM_CALL becomes SYSLOG_FROM_READER, and +SYSLOG_FROM_FILE becomes SYSLOG_FROM_PROC). SYSLOG_FROM_READER allows +non-destructive actions, and SYSLOG_FROM_PROC allows destructive actions +after a capabilities-constrained SYSLOG_ACTION_OPEN check. + +- /dev/kmsg allows: + - open if CAP_SYSLOG or dmesg_restrict==0 + - reading/polling, after open + +Signed-off-by: Kees Cook Reported-by: Christian Kujau -CC: stable@vger.kernel.org -Signed-off-by: Eric Paris -Signed-off-by: Josh Boyer +Cc: Josh Boyer +Cc: Kay Sievers +Cc: stable@vger.kernel.org --- - kernel/printk.c | 91 +++++++++++++++++++++++++++++---------------------------- - 1 file changed, 47 insertions(+), 44 deletions(-) + fs/proc/kmsg.c | 10 +++--- + include/linux/syslog.h | 4 +-- + kernel/printk.c | 91 ++++++++++++++++++++++++++---------------------- + 3 files changed, 57 insertions(+), 48 deletions(-) +diff --git a/fs/proc/kmsg.c b/fs/proc/kmsg.c +index bd4b5a7..bdfabda 100644 +--- a/fs/proc/kmsg.c ++++ b/fs/proc/kmsg.c +@@ -21,12 +21,12 @@ extern wait_queue_head_t log_wait; + + static int kmsg_open(struct inode * inode, struct file * file) + { +- return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_FILE); ++ return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC); + } + + static int kmsg_release(struct inode * inode, struct file * file) + { +- (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_FILE); ++ (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC); + return 0; + } + +@@ -34,15 +34,15 @@ static ssize_t kmsg_read(struct file *file, char __user *buf, + size_t count, loff_t *ppos) + { + if ((file->f_flags & O_NONBLOCK) && +- !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_FILE)) ++ !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) + return -EAGAIN; +- return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_FILE); ++ return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC); + } + + static unsigned int kmsg_poll(struct file *file, poll_table *wait) + { + poll_wait(file, &log_wait, wait); +- if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_FILE)) ++ if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) + return POLLIN | POLLRDNORM; + return 0; + } +diff --git a/include/linux/syslog.h b/include/linux/syslog.h +index 3891139..98a3153 100644 +--- a/include/linux/syslog.h ++++ b/include/linux/syslog.h +@@ -44,8 +44,8 @@ + /* Return size of the log buffer */ + #define SYSLOG_ACTION_SIZE_BUFFER 10 + +-#define SYSLOG_FROM_CALL 0 +-#define SYSLOG_FROM_FILE 1 ++#define SYSLOG_FROM_READER 0 ++#define SYSLOG_FROM_PROC 1 + + int do_syslog(int type, char __user *buf, int count, bool from_file); + diff --git a/kernel/printk.c b/kernel/printk.c -index abbdd9e..5541095 100644 +index abbdd9e..53b5c5e 100644 --- a/kernel/printk.c +++ b/kernel/printk.c -@@ -368,6 +368,46 @@ static void log_store(int facility, int level, +@@ -368,6 +368,53 @@ static void log_store(int facility, int level, log_next_seq++; } @@ -41,8 +114,12 @@ index abbdd9e..5541095 100644 +{ + 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; ++ /* ++ * 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) @@ -52,55 +129,42 @@ index abbdd9e..5541095 100644 + * already done the capabilities checks at open time. + */ + if (from_file && type != SYSLOG_ACTION_OPEN) -+ goto ok; ++ return 0; + + if (syslog_action_restricted(type)) { + if (capable(CAP_SYSLOG)) -+ goto ok; -+ /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ ++ 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)); -+ goto ok; ++ return 0; + } + 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) +@@ -624,7 +671,8 @@ 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); ++ err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, ++ SYSLOG_FROM_READER); if (err) return err; -@@ -817,45 +863,6 @@ static inline void boot_delay_msec(int level) +@@ -817,45 +865,6 @@ static inline void boot_delay_msec(int level) } #endif @@ -146,17 +210,19 @@ index abbdd9e..5541095 100644 #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; +@@ -1253,7 +1262,7 @@ out: -- error = security_syslog(type); -- if (error) -- return error; -- - switch (type) { - case SYSLOG_ACTION_CLOSE: /* Close log */ - break; + SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) + { +- return do_syslog(type, buf, len, SYSLOG_FROM_CALL); ++ return do_syslog(type, buf, len, SYSLOG_FROM_READER); + } + + /* -- -1.8.1.4 +1.7.9.5 + +-- +Kees Cook +Chrome OS Security diff --git a/kernel.spec b/kernel.spec index b820a6a5c..a396c1c68 100644 --- a/kernel.spec +++ b/kernel.spec @@ -2240,6 +2240,9 @@ fi # ||----w | # || || %changelog +* Tue May 07 2013 Josh Boyer +- Fix dmesg_restrict patch to avoid regression (rhbz 952655) + * Mon May 06 2013 Josh Boyer - 3.10.0-0.rc0.git19.1 - Linux v3.9-10936-g51a26ae