[PATCH 3/3] comm: ext4: Protect task->comm access by using get_task_comm()

[John Stultz]

Converts ext4 comm access to use the safe get_task_comm accessor.

CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: David Rientjes <rientjes@xxxxxxxxxx>
CC: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
 fs/ext4/file.c  |    8 ++++++--
 fs/ext4/super.c |   13 ++++++++++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 7b80d54..d37414e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -124,11 +124,15 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 		static unsigned long unaligned_warn_time;
 
 		/* Warn about this once per day */
-		if (printk_timed_ratelimit(&unaligned_warn_time, 60*60*24*HZ))
+		if (printk_timed_ratelimit(&unaligned_warn_time, 60*60*24*HZ)) {
+			char comm[TASK_COMM_LEN];
+
+			get_task_comm(comm, current);
 			ext4_msg(inode->i_sb, KERN_WARNING,
 				 "Unaligned AIO/DIO on inode %ld by %s; "
 				 "performance will be poor.",
-				 inode->i_ino, current->comm);
+				 inode->i_ino, comm);
+		}
 		mutex_lock(ext4_aio_mutex(inode));
 		ext4_aiodio_wait(inode);
 	}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8553dfb..6c9151f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -409,12 +409,15 @@ void __ext4_error(struct super_block *sb, const char *function,
 {
 	struct va_format vaf;
 	va_list args;
+	char comm[TASK_COMM_LEN];
 
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
+
+	get_task_comm(comm, current);
 	printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: comm %s: %pV\n",
-	       sb->s_id, function, line, current->comm, &vaf);
+	       sb->s_id, function, line, comm, &vaf);
 	va_end(args);
 
 	ext4_handle_error(sb);
@@ -427,6 +430,7 @@ void ext4_error_inode(struct inode *inode, const char *function,
 	va_list args;
 	struct va_format vaf;
 	struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
+	char comm[TASK_COMM_LEN];
 
 	es->s_last_error_ino = cpu_to_le32(inode->i_ino);
 	es->s_last_error_block = cpu_to_le64(block);
@@ -438,7 +442,8 @@ void ext4_error_inode(struct inode *inode, const char *function,
 	       inode->i_sb->s_id, function, line, inode->i_ino);
 	if (block)
 		printk(KERN_CONT "block %llu: ", block);
-	printk(KERN_CONT "comm %s: %pV\n", current->comm, &vaf);
+	get_task_comm(comm, current);
+	printk(KERN_CONT "comm %s: %pV\n", comm, &vaf);
 	va_end(args);
 
 	ext4_handle_error(inode->i_sb);
@@ -453,6 +458,7 @@ void ext4_error_file(struct file *file, const char *function,
 	struct ext4_super_block *es;
 	struct inode *inode = file->f_dentry->d_inode;
 	char pathname[80], *path;
+	char comm[TASK_COMM_LEN];
 
 	es = EXT4_SB(inode->i_sb)->s_es;
 	es->s_last_error_ino = cpu_to_le32(inode->i_ino);
@@ -468,7 +474,8 @@ void ext4_error_file(struct file *file, const char *function,
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
-	printk(KERN_CONT "comm %s: path %s: %pV\n", current->comm, path, &vaf);
+	get_task_comm(comm, current);
+	printk(KERN_CONT "comm %s: path %s: %pV\n", comm, path, &vaf);
 	va_end(args);
 
 	ext4_handle_error(inode->i_sb);
-- 
1.7.3.2.146.gca209

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