ext4: fix #11321: create /proc/ext4/*/stats more carefully

(cherry picked from commit 899fc1a4cf404747de2666534d508804597ee22f)

ext4 creates per-suberblock directory in /proc/ext4/ . Name used as
basis is taken from bdevname, which, surprise, can contain slash.

However, proc while allowing to use proc_create("a/b", parent) form of
PDE creation, assumes that parent/a was already created.

bdevname in question is 'cciss/c0d0p9', directory is not created and all
this stuff goes directly into /proc (which is real bug).

Warning comes when _second_ partition is mounted.

http://bugzilla.kernel.org/show_bug.cgi?id=11321

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index e0e3a5eb1ddba0575798cd5d561b23c25409cdb6..0d51106b17c8e9b32584627487bf7ffa65de1bea 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2785,14 +2785,20 @@ static int ext4_mb_init_per_dev_proc(struct super_block *sb)
        mode_t mode = S_IFREG | S_IRUGO | S_IWUSR;
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct proc_dir_entry *proc;
-       char devname[64];
+       char devname[BDEVNAME_SIZE], *p;
 
        if (proc_root_ext4 == NULL) {
                sbi->s_mb_proc = NULL;
                return -EINVAL;
        }
        bdevname(sb->s_bdev, devname);
+       p = devname;
+       while ((p = strchr(p, '/')))
+               *p = '!';
+
        sbi->s_mb_proc = proc_mkdir(devname, proc_root_ext4);
+       if (!sbi->s_mb_proc)
+               goto err_create_dir;
 
        MB_PROC_HANDLER(EXT4_MB_STATS_NAME, stats);
        MB_PROC_HANDLER(EXT4_MB_MAX_TO_SCAN_NAME, max_to_scan);
@@ -2804,7 +2810,6 @@ static int ext4_mb_init_per_dev_proc(struct super_block *sb)
        return 0;
 
 err_out:
-       printk(KERN_ERR "EXT4-fs: Unable to create %s\n", devname);
        remove_proc_entry(EXT4_MB_GROUP_PREALLOC, sbi->s_mb_proc);
        remove_proc_entry(EXT4_MB_STREAM_REQ, sbi->s_mb_proc);
        remove_proc_entry(EXT4_MB_ORDER2_REQ, sbi->s_mb_proc);
@@ -2813,6 +2818,8 @@ err_out:
        remove_proc_entry(EXT4_MB_STATS_NAME, sbi->s_mb_proc);
        remove_proc_entry(devname, proc_root_ext4);
        sbi->s_mb_proc = NULL;
+err_create_dir:
+       printk(KERN_ERR "EXT4-fs: Unable to create %s\n", devname);
 
        return -ENOMEM;
 }
@@ -2820,12 +2827,15 @@ err_out:
 static int ext4_mb_destroy_per_dev_proc(struct super_block *sb)
 {
        struct ext4_sb_info *sbi = EXT4_SB(sb);
-       char devname[64];
+       char devname[BDEVNAME_SIZE], *p;
 
        if (sbi->s_mb_proc == NULL)
                return -EINVAL;
 
        bdevname(sb->s_bdev, devname);
+       p = devname;
+       while ((p = strchr(p, '/')))
+               *p = '!';
        remove_proc_entry(EXT4_MB_GROUP_PREALLOC, sbi->s_mb_proc);
        remove_proc_entry(EXT4_MB_STREAM_REQ, sbi->s_mb_proc);
        remove_proc_entry(EXT4_MB_ORDER2_REQ, sbi->s_mb_proc);