Messages in this thread Patch in this message | | | Subject | [PATCH] 2.6.22-rc6-mm1: hugetlbfs handle empty options string | From | Lee Schermerhorn <> | Date | Tue, 10 Jul 2007 15:59:00 -0400 |
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[PATCH] 2.6.22-rc6-mm1 - hugetlbfs handle empty options string
I was seeing a null pointer deref in fs/super.c:vfs_kern_mount(). Some file system get_sb() handler was returning NULL mnt_sb with a non-negative return value. I also noticed a "hugetlbfs: Bad mount option:" message in the log.
Turns out that hugetlbfs_parse_options() was not checking for an empty option string after call to strsep(). On failure, hugetlbfs_parse_options() returns 1. hugetlbfs_fill_super() just passed this return code back up the call stack where vfs_kern_mount() missed the error and proceeded with a NULL mnt_sb.
Apparently introduced by patch: hugetlbfs-use-lib-parser-fix-docs.patch
The problem was exposed by this line in my fstab:
none /huge hugetlbfs defaults 0 0
It can also be demonstrated by invoking mount of hugetlbfs directly with no options or a bogus option.
This patch:
1) adds the check for empty option to hugetlbfs_parse_options(), 2) enhances the error message to bracket any unrecognized option with quotes , 3) modifies hugetlbfs_parse_options() to return -EINVAL on any unrecognized option, 4) adds a BUG_ON() to vfs_kern_mount() to catch any get_sb() handler that returns a NULL mnt->mnt_sb with a return value >= 0.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
fs/hugetlbfs/inode.c | 8 +++++--- fs/super.c | 1 + 2 files changed, 6 insertions(+), 3 deletions(-)
Index: Linux/fs/hugetlbfs/inode.c =================================================================== --- Linux.orig/fs/hugetlbfs/inode.c 2007-07-10 14:49:31.000000000 -0400 +++ Linux/fs/hugetlbfs/inode.c 2007-07-10 15:10:28.000000000 -0400 @@ -625,6 +625,8 @@ hugetlbfs_parse_options(char *options, s while ((p = strsep(&options, ",")) != NULL) { int token; + if (!*p) + continue; token = match_token(p, tokens, args); switch (token) { @@ -669,8 +671,9 @@ hugetlbfs_parse_options(char *options, s break; default: - printk(KERN_ERR "hugetlbfs: Bad mount option: %s\n", p); - return 1; + printk(KERN_ERR "hugetlbfs: Bad mount option: \"%s\"\n", + p); + return -EINVAL; break; } } @@ -697,7 +700,6 @@ hugetlbfs_fill_super(struct super_block config.gid = current->fsgid; config.mode = 0755; ret = hugetlbfs_parse_options(data, &config); - if (ret) return ret; Index: Linux/fs/super.c =================================================================== --- Linux.orig/fs/super.c 2007-07-10 14:49:32.000000000 -0400 +++ Linux/fs/super.c 2007-07-10 15:00:46.000000000 -0400 @@ -880,6 +880,7 @@ vfs_kern_mount(struct file_system_type * error = type->get_sb(type, flags, name, data, mnt); if (error < 0) goto out_free_secdata; + BUG_ON(!mnt->mnt_sb); error = security_sb_kern_mount(mnt->mnt_sb, secdata); if (error)
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