[LU-1411] panic in lmd_parse() on kernels < 2.6.18

Fri, 5 Dec 2014 18:52:08 +0000

We've begun testing the Lustre 2.1 client on our BlueGene P development system.

It immediately panicked on the first mount attempt. This turns out to be related to a patch landed for ~~LU-163~~. lustre_get_sb() conditionally calls get_sb_nodev() with a struct lustre_mount_data2 * for kernels 2.6.18 and newer, and a void * data pointer for older kernels:

2196 #if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,18))
2197 struct super_block * lustre_get_sb(struct file_system_type *fs_type, int flags,
2198                                    const char *devname, void * data)
2199 {
2200         return get_sb_nodev(fs_type, flags, data, lustre_fill_super);
2201 }
2202 #else
2203 int lustre_get_sb(struct file_system_type *fs_type, int flags,
2204                   const char *devname, void * data, struct vfsmount *mnt)
2205 {
2206         struct lustre_mount_data2 lmd2 = {data, mnt};
2207 
2208         return get_sb_nodev(fs_type, flags, &lmd2, lustre_fill_super, mnt);
2209 }
2210 #endif

However, lustre_fill_super() unconditionally casts its void *data argument to a struct lustre_mount_data2 *, which causes a crash when we deference into it on older kernels.

1945 /** Parse mount line options
1946  * e.g. mount -v -t lustre -o abort_recov uml1:uml2:/lustre-client /mnt/lustre
1947  * dev is passed as device=uml1:/lustre by mount.lustre
1948  */
1949 static int lmd_parse(char *options, struct lustre_mount_data *lmd)
1950 {
1951         char *s1, *s2, *devname = NULL;
1952         struct lustre_mount_data *raw = (struct lustre_mount_data *)options;
...
1963         /* Options should be a string - try to detect old lmd data */
1964         if ((raw->lmd_magic & 0xffffff00) == (LMD_MAGIC & 0xffffff00)) { <--- crashes here

...

2102 int lustre_fill_super(struct super_block *sb, void *data, int silent)
2103 {
2104         struct lustre_mount_data *lmd;
2105         struct lustre_mount_data2 *lmd2 = data;
...
2122 
2123         /* Figure out the lmd from the mount options */
2124         if (lmd_parse((char *)(lmd2->lmd2_data), lmd)) {

Whamcloud Community JIRA

[LU-1411] panic in lmd_parse() on kernels < 2.6.18