android: logger: Allow a UID to read it's own log entries

staging: logger: hold mutex while removing reader staging: android: logger: clarify non-update of w_off in do_write_log_from_user staging: android: logger: clarify code in clock_interval staging: android: logger: reorder prepare_to_wait and mutex_lock staging: android: logger: simplify and optimize get_entry_len staging: android: logger: Change logger_offset() from macro to function Staging: android: fixed white spaces coding style issue in logger.c android: logger: bump up the logger buffer sizes
2012-08-15 14:56:37 +08:00
parent d6b41b0def
commit 9c3257d859
3 changed files with 249 additions and 54 deletions
--- a/drivers/staging/android/logger.c
+++ b/drivers/staging/android/logger.c
@@ -37,7 +37,7 @@
 * mutex 'mutex'.
 */
 struct logger_log {
-	unsigned char 		*buffer;/* the ring buffer itself */
+	unsigned char		*buffer;/* the ring buffer itself */
 	struct miscdevice	misc;	/* misc device representing the log */
 	wait_queue_head_t	wq;	/* wait queue for readers */
 	struct list_head	readers; /* this log's readers */
@@ -57,19 +57,25 @@ struct logger_reader {
 	struct logger_log	*log;	/* associated log */
 	struct list_head	list;	/* entry in logger_log's list */
 	size_t			r_off;	/* current read head offset */
+	bool			r_all;	/* reader can read all entries */
+	int			r_ver;	/* reader ABI version */
 };

 /* logger_offset - returns index 'n' into the log via (optimized) modulus */
-#define logger_offset(n)	((n) & (log->size - 1))
+size_t logger_offset(struct logger_log *log, size_t n)
+{
+	return n & (log->size-1);
+}
+

 /*
 * file_get_log - Given a file structure, return the associated log
 *
 * This isn't aesthetic. We have several goals:
 *
- * 	1) Need to quickly obtain the associated log during an I/O operation
- * 	2) Readers need to maintain state (logger_reader)
- * 	3) Writers need to be very fast (open() should be a near no-op)
+ *	1) Need to quickly obtain the associated log during an I/O operation
+ *	2) Readers need to maintain state (logger_reader)
+ *	3) Writers need to be very fast (open() should be a near no-op)
 *
 * In the reader case, we can trivially go file->logger_reader->logger_log.
 * For a writer, we don't want to maintain a logger_reader, so we just go
@@ -86,25 +92,75 @@ static inline struct logger_log *file_get_log(struct file *file)
 }

 /*
- * get_entry_len - Grabs the length of the payload of the next entry starting
- * from 'off'.
+ * get_entry_header - returns a pointer to the logger_entry header within
+ * 'log' starting at offset 'off'. A temporary logger_entry 'scratch' must
+ * be provided. Typically the return value will be a pointer within
+ * 'logger->buf'.  However, a pointer to 'scratch' may be returned if
+ * the log entry spans the end and beginning of the circular buffer.
+ */
+static struct logger_entry *get_entry_header(struct logger_log *log,
+		size_t off, struct logger_entry *scratch)
+{
+	size_t len = min(sizeof(struct logger_entry), log->size - off);
+	if (len != sizeof(struct logger_entry)) {
+		memcpy(((void *) scratch), log->buffer + off, len);
+		memcpy(((void *) scratch) + len, log->buffer,
+			sizeof(struct logger_entry) - len);
+		return scratch;
+	}
+
+	return (struct logger_entry *) (log->buffer + off);
+}
+
+/*
+ * get_entry_msg_len - Grabs the length of the message of the entry
+ * starting from from 'off'.
+ *
+ * An entry length is 2 bytes (16 bits) in host endian order.
+ * In the log, the length does not include the size of the log entry structure.
+ * This function returns the size including the log entry structure.
 *
 * Caller needs to hold log->mutex.
 */
-static __u32 get_entry_len(struct logger_log *log, size_t off)
+static __u32 get_entry_msg_len(struct logger_log *log, size_t off)
 {
-	__u16 val;
+	struct logger_entry scratch;
+	struct logger_entry *entry;

-	switch (log->size - off) {
-	case 1:
-		memcpy(&val, log->buffer + off, 1);
-		memcpy(((char *) &val) + 1, log->buffer, 1);
-		break;
-	default:
-		memcpy(&val, log->buffer + off, 2);
+	entry = get_entry_header(log, off, &scratch);
+	return entry->len;
+}
+
+static size_t get_user_hdr_len(int ver)
+{
+	if (ver < 2)
+		return sizeof(struct user_logger_entry_compat);
+	else
+		return sizeof(struct logger_entry);
+}
+
+static ssize_t copy_header_to_user(int ver, struct logger_entry *entry,
+					 char __user *buf)
+{
+	void *hdr;
+	size_t hdr_len;
+	struct user_logger_entry_compat v1;
+
+	if (ver < 2) {
+		v1.len      = entry->len;
+		v1.__pad    = 0;
+		v1.pid      = entry->pid;
+		v1.tid      = entry->tid;
+		v1.sec      = entry->sec;
+		v1.nsec     = entry->nsec;
+		hdr         = &v1;
+		hdr_len     = sizeof(struct user_logger_entry_compat);
+	} else {
+		hdr         = entry;
+		hdr_len     = sizeof(struct logger_entry);
 	}

-	return sizeof(struct logger_entry) + val;
+	return copy_to_user(buf, hdr, hdr_len);
 }

 /*
@@ -118,15 +174,31 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
 				   char __user *buf,
 				   size_t count)
 {
+	struct logger_entry scratch;
+	struct logger_entry *entry;
 	size_t len;
+	size_t msg_start;

 	/*
-	 * We read from the log in two disjoint operations. First, we read from
-	 * the current read head offset up to 'count' bytes or to the end of
+	 * First, copy the header to userspace, using the version of
+	 * the header requested
+	 */
+	entry = get_entry_header(log, reader->r_off, &scratch);
+	if (copy_header_to_user(reader->r_ver, entry, buf))
+		return -EFAULT;
+
+	count -= get_user_hdr_len(reader->r_ver);
+	buf += get_user_hdr_len(reader->r_ver);
+	msg_start = logger_offset(log,
+		reader->r_off + sizeof(struct logger_entry));
+
+	/*
+	 * We read from the msg in two disjoint operations. First, we read from
+	 * the current msg head offset up to 'count' bytes or to the end of
 	 * the log, whichever comes first.
 	 */
-	len = min(count, log->size - reader->r_off);
-	if (copy_to_user(buf, log->buffer + reader->r_off, len))
+	len = min(count, log->size - msg_start);
+	if (copy_to_user(buf, log->buffer + msg_start, len))
 		return -EFAULT;

 	/*
@@ -137,9 +209,34 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
 		if (copy_to_user(buf + len, log->buffer, count - len))
 			return -EFAULT;

-	reader->r_off = logger_offset(reader->r_off + count);
+	reader->r_off = logger_offset(log, reader->r_off +
+		sizeof(struct logger_entry) + count);

-	return count;
+	return count + get_user_hdr_len(reader->r_ver);
+}
+
+/*
+ * get_next_entry_by_uid - Starting at 'off', returns an offset into
+ * 'log->buffer' which contains the first entry readable by 'euid'
+ */
+static size_t get_next_entry_by_uid(struct logger_log *log,
+		size_t off, uid_t euid)
+{
+	while (off != log->w_off) {
+		struct logger_entry *entry;
+		struct logger_entry scratch;
+		size_t next_len;
+
+		entry = get_entry_header(log, off, &scratch);
+
+		if (entry->euid == euid)
+			return off;
+
+		next_len = sizeof(struct logger_entry) + entry->len;
+		off = logger_offset(log, off + next_len);
+	}
+
+	return off;
 }

 /*
@@ -147,11 +244,11 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
 *
 * Behavior:
 *
- * 	- O_NONBLOCK works
- * 	- If there are no log entries to read, blocks until log is written to
- * 	- Atomically reads exactly one log entry
+ *	- O_NONBLOCK works
+ *	- If there are no log entries to read, blocks until log is written to
+ *	- Atomically reads exactly one log entry
 *
- * Optimal read size is LOGGER_ENTRY_MAX_LEN. Will set errno to EINVAL if read
+ * Will set errno to EINVAL if read
 * buffer is insufficient to hold next entry.
 */
 static ssize_t logger_read(struct file *file, char __user *buf,
@@ -164,9 +261,10 @@ static ssize_t logger_read(struct file *file, char __user *buf,

 start:
 	while (1) {
+		mutex_lock(&log->mutex);
+
 		prepare_to_wait(&log->wq, &wait, TASK_INTERRUPTIBLE);

-		mutex_lock(&log->mutex);
 		ret = (log->w_off == reader->r_off);
 		mutex_unlock(&log->mutex);
 		if (!ret)
@@ -191,6 +289,10 @@ start:

 	mutex_lock(&log->mutex);

+	if (!reader->r_all)
+		reader->r_off = get_next_entry_by_uid(log,
+			reader->r_off, current_euid());
+
 	/* is there still something to read or did we race? */
 	if (unlikely(log->w_off == reader->r_off)) {
 		mutex_unlock(&log->mutex);
@@ -198,7 +300,8 @@ start:
 	}

 	/* get the size of the next entry */
-	ret = get_entry_len(log, reader->r_off);
+	ret = get_user_hdr_len(reader->r_ver) +
+		get_entry_msg_len(log, reader->r_off);
 	if (count < ret) {
 		ret = -EINVAL;
 		goto out;
@@ -224,8 +327,9 @@ static size_t get_next_entry(struct logger_log *log, size_t off, size_t len)
 	size_t count = 0;

 	do {
-		size_t nr = get_entry_len(log, off);
-		off = logger_offset(off + nr);
+		size_t nr = sizeof(struct logger_entry) +
+			get_entry_msg_len(log, off);
+		off = logger_offset(log, off + nr);
 		count += nr;
 	} while (count < len);

@@ -233,16 +337,28 @@ static size_t get_next_entry(struct logger_log *log, size_t off, size_t len)
 }

 /*
- * clock_interval - is a < c < b in mod-space? Put another way, does the line
- * from a to b cross c?
+ * is_between - is a < c < b, accounting for wrapping of a, b, and c
+ *    positions in the buffer
+ *
+ * That is, if a<b, check for c between a and b
+ * and if a>b, check for c outside (not between) a and b
+ *
+ * |------- a xxxxxxxx b --------|
+ *               c^
+ *
+ * |xxxxx b --------- a xxxxxxxxx|
+ *    c^
+ *  or                    c^
 */
-static inline int clock_interval(size_t a, size_t b, size_t c)
+static inline int is_between(size_t a, size_t b, size_t c)
 {
-	if (b < a) {
-		if (a < c || b >= c)
+	if (a < b) {
+		/* is c between a and b? */
+		if (a < c && c <= b)
 			return 1;
 	} else {
-		if (a < c && b >= c)
+		/* is c outside of b through a? */
+		if (c <= b || a < c)
 			return 1;
 	}

@@ -260,14 +376,14 @@ static inline int clock_interval(size_t a, size_t b, size_t c)
 static void fix_up_readers(struct logger_log *log, size_t len)
 {
 	size_t old = log->w_off;
-	size_t new = logger_offset(old + len);
+	size_t new = logger_offset(log, old + len);
 	struct logger_reader *reader;

-	if (clock_interval(old, new, log->head))
+	if (is_between(old, new, log->head))
 		log->head = get_next_entry(log, log->head, len);

 	list_for_each_entry(reader, &log->readers, list)
-		if (clock_interval(old, new, reader->r_off))
+		if (is_between(old, new, reader->r_off))
 			reader->r_off = get_next_entry(log, reader->r_off, len);
 }

@@ -286,7 +402,7 @@ static void do_write_log(struct logger_log *log, const void *buf, size_t count)
 	if (count != len)
 		memcpy(log->buffer, buf + len, count - len);

-	log->w_off = logger_offset(log->w_off + count);
+	log->w_off = logger_offset(log, log->w_off + count);

 }

@@ -309,9 +425,15 @@ static ssize_t do_write_log_from_user(struct logger_log *log,

 	if (count != len)
 		if (copy_from_user(log->buffer, buf + len, count - len))
+			/*
+			 * Note that by not updating w_off, this abandons the
+			 * portion of the new entry that *was* successfully
+			 * copied, just above.  This is intentional to avoid
+			 * message corruption from missing fragments.
+			 */
 			return -EFAULT;

-	log->w_off = logger_offset(log->w_off + count);
+	log->w_off = logger_offset(log, log->w_off + count);

 	return count;
 }
@@ -336,7 +458,9 @@ ssize_t logger_aio_write(struct kiocb *iocb, const struct iovec *iov,
 	header.tid = current->pid;
 	header.sec = now.tv_sec;
 	header.nsec = now.tv_nsec;
+	header.euid = current_euid();
 	header.len = min_t(size_t, iocb->ki_left, LOGGER_ENTRY_MAX_PAYLOAD);
+	header.hdr_size = sizeof(struct logger_entry);

 	/* null writes succeed, return zero */
 	if (unlikely(!header.len))
@@ -409,6 +533,10 @@ static int logger_open(struct inode *inode, struct file *file)
 			return -ENOMEM;

 		reader->log = log;
+		reader->r_ver = 1;
+		reader->r_all = in_egroup_p(inode->i_gid) ||
+			capable(CAP_SYSLOG);
+
 		INIT_LIST_HEAD(&reader->list);

 		mutex_lock(&log->mutex);
@@ -433,9 +561,11 @@ static int logger_release(struct inode *ignored, struct file *file)
 	if (file->f_mode & FMODE_READ) {
 		struct logger_reader *reader = file->private_data;
 		struct logger_log *log = reader->log;
+
 		mutex_lock(&log->mutex);
 		list_del(&reader->list);
 		mutex_unlock(&log->mutex);
+
 		kfree(reader);
 	}

@@ -466,6 +596,10 @@ static unsigned int logger_poll(struct file *file, poll_table *wait)
 	poll_wait(file, &log->wq, wait);

 	mutex_lock(&log->mutex);
+	if (!reader->r_all)
+		reader->r_off = get_next_entry_by_uid(log,
+			reader->r_off, current_euid());
+
 	if (log->w_off != reader->r_off)
 		ret |= POLLIN | POLLRDNORM;
 	mutex_unlock(&log->mutex);
@@ -473,11 +607,25 @@ static unsigned int logger_poll(struct file *file, poll_table *wait)
 	return ret;
 }

+static long logger_set_version(struct logger_reader *reader, void __user *arg)
+{
+	int version;
+	if (copy_from_user(&version, arg, sizeof(int)))
+		return -EFAULT;
+
+	if ((version < 1) || (version > 2))
+		return -EINVAL;
+
+	reader->r_ver = version;
+	return 0;
+}
+
 static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct logger_log *log = file_get_log(file);
 	struct logger_reader *reader;
-	long ret = -ENOTTY;
+	long ret = -EINVAL;
+	void __user *argp = (void __user *) arg;

 	mutex_lock(&log->mutex);

@@ -502,8 +650,14 @@ static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 			break;
 		}
 		reader = file->private_data;
+
+		if (!reader->r_all)
+			reader->r_off = get_next_entry_by_uid(log,
+				reader->r_off, current_euid());
+
 		if (log->w_off != reader->r_off)
-			ret = get_entry_len(log, reader->r_off);
+			ret = get_user_hdr_len(reader->r_ver) +
+				get_entry_msg_len(log, reader->r_off);
 		else
 			ret = 0;
 		break;
@@ -517,6 +671,22 @@ static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		log->head = log->w_off;
 		ret = 0;
 		break;
+	case LOGGER_GET_VERSION:
+		if (!(file->f_mode & FMODE_READ)) {
+			ret = -EBADF;
+			break;
+		}
+		reader = file->private_data;
+		ret = reader->r_ver;
+		break;
+	case LOGGER_SET_VERSION:
+		if (!(file->f_mode & FMODE_READ)) {
+			ret = -EBADF;
+			break;
+		}
+		reader = file->private_data;
+		ret = logger_set_version(reader, argp);
+		break;
 	}

 	mutex_unlock(&log->mutex);
@@ -537,8 +707,8 @@ static const struct file_operations logger_fops = {

 /*
 * Defines a log structure with name 'NAME' and a size of 'SIZE' bytes, which
- * must be a power of two, greater than LOGGER_ENTRY_MAX_LEN, and less than
- * LONG_MAX minus LOGGER_ENTRY_MAX_LEN.
+ * must be a power of two, and greater than
+ * (LOGGER_ENTRY_MAX_PAYLOAD + sizeof(struct logger_entry)).
 */
 #define DEFINE_LOGGER_DEVICE(VAR, NAME, SIZE) \
 static unsigned char _buf_ ## VAR[SIZE]; \
@@ -558,10 +728,10 @@ static struct logger_log VAR = { \
 	.size = SIZE, \
 };

-DEFINE_LOGGER_DEVICE(log_main, LOGGER_LOG_MAIN, 64*1024)
+DEFINE_LOGGER_DEVICE(log_main, LOGGER_LOG_MAIN, 256*1024)
 DEFINE_LOGGER_DEVICE(log_events, LOGGER_LOG_EVENTS, 256*1024)
-DEFINE_LOGGER_DEVICE(log_radio, LOGGER_LOG_RADIO, 64*1024)
-DEFINE_LOGGER_DEVICE(log_system, LOGGER_LOG_SYSTEM, 64*1024)
+DEFINE_LOGGER_DEVICE(log_radio, LOGGER_LOG_RADIO, 256*1024)
+DEFINE_LOGGER_DEVICE(log_system, LOGGER_LOG_SYSTEM, 256*1024)

 static struct logger_log *get_log_from_minor(int minor)
 {
--- a/drivers/staging/android/logger.h
+++ b/drivers/staging/android/logger.h
@@ -20,7 +20,12 @@
 #include <linux/types.h>
 #include <linux/ioctl.h>

-struct logger_entry {
+/*
+ * The userspace structure for version 1 of the logger_entry ABI.
+ * This structure is returned to userspace unless the caller requests
+ * an upgrade to a newer ABI version.
+ */
+struct user_logger_entry_compat {
 	__u16		len;	/* length of the payload */
 	__u16		__pad;	/* no matter what, we get 2 bytes of padding */
 	__s32		pid;	/* generating process's pid */
@@ -30,14 +35,28 @@ struct logger_entry {
 	char		msg[0];	/* the entry's payload */
 };

+/*
+ * The structure for version 2 of the logger_entry ABI.
+ * This structure is returned to userspace if ioctl(LOGGER_SET_VERSION)
+ * is called with version >= 2
+ */
+struct logger_entry {
+	__u16		len;		/* length of the payload */
+	__u16		hdr_size;	/* sizeof(struct logger_entry_v2) */
+	__s32		pid;		/* generating process's pid */
+	__s32		tid;		/* generating process's tid */
+	__s32		sec;		/* seconds since Epoch */
+	__s32		nsec;		/* nanoseconds */
+	uid_t		euid;		/* effective UID of logger */
+	char		msg[0];		/* the entry's payload */
+};
+
 #define LOGGER_LOG_RADIO	"log_radio"	/* radio-related messages */
 #define LOGGER_LOG_EVENTS	"log_events"	/* system/hardware events */
 #define LOGGER_LOG_SYSTEM	"log_system"	/* system/framework messages */
 #define LOGGER_LOG_MAIN		"log_main"	/* everything else */

-#define LOGGER_ENTRY_MAX_LEN		(4*1024)
-#define LOGGER_ENTRY_MAX_PAYLOAD	\
-	(LOGGER_ENTRY_MAX_LEN - sizeof(struct logger_entry))
+#define LOGGER_ENTRY_MAX_PAYLOAD	4076

 #define __LOGGERIO	0xAE

@@ -45,5 +64,7 @@ struct logger_entry {
 #define LOGGER_GET_LOG_LEN		_IO(__LOGGERIO, 2) /* used log len */
 #define LOGGER_GET_NEXT_ENTRY_LEN	_IO(__LOGGERIO, 3) /* next entry len */
 #define LOGGER_FLUSH_LOG		_IO(__LOGGERIO, 4) /* flush log */
+#define LOGGER_GET_VERSION		_IO(__LOGGERIO, 5) /* abi version */
+#define LOGGER_SET_VERSION		_IO(__LOGGERIO, 6) /* abi version */

 #endif /* _LINUX_LOGGER_H */
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -357,7 +357,11 @@ struct cpu_vfs_cap_data {

 #define CAP_MAC_ADMIN        33

-#define CAP_LAST_CAP         CAP_MAC_ADMIN
+/* Allow configuring the kernel's syslog (printk behaviour) */
+
+#define CAP_SYSLOG           34
+
+#define CAP_LAST_CAP         CAP_SYSLOG

 #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)