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

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>

1 files changed, 13 insertions, 3 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 585c25950184..9122271e3d65 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2786,14 +2786,20 @@ 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);
@@ -2805,7 +2811,6 @@ 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);
@@ -2814,6 +2819,8 @@ 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;
 }
@@ -2821,12 +2828,15 @@ 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);