From d251ed271d528afb407cc2ede30923e34cb209a5 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 12 Jun 2011 10:24:33 -0400 Subject: [PATCH] ubifs: fix sget races * allocate ubifs_info in ->mount(), fill it enough for sb_test() and set ->s_fs_info to it in set() callback passed to sget(). * do *not* free it in ->put_super(); do that in ->kill_sb() after we'd done kill_anon_super(). * don't free it in ubifs_fill_super() either - deactivate_locked_super() done by caller when ubifs_fill_super() returns an error will take care of that sucker. * get rid of kludge with passing ubi to ubifs_fill_super() in ->s_fs_info; we only need it in alloc_ubifs_info(), so ubifs_fill_super() will need only ubifs_info. Which it will find in ->s_fs_info just fine, no need to reassign anything... As the result, sb_test() becomes safe to apply to all superblocks that can be found by sget() (and a kludge with temporary use of ->s_fs_info to store a pointer to very different structure goes away). Signed-off-by: Al Viro --- fs/ubifs/super.c | 54 +++++++++++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 24 deletions(-) diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c index ddc3b02e8cf0..8c892c2d5300 100644 --- a/fs/ubifs/super.c +++ b/fs/ubifs/super.c @@ -1848,7 +1848,6 @@ static void ubifs_put_super(struct super_block *sb) bdi_destroy(&c->bdi); ubi_close_volume(c->ubi); mutex_unlock(&c->umount_mutex); - kfree(c); } static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data) @@ -2020,21 +2019,16 @@ static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi) static int ubifs_fill_super(struct super_block *sb, void *data, int silent) { - struct ubi_volume_desc *ubi = sb->s_fs_info; - struct ubifs_info *c; + struct ubifs_info *c = sb->s_fs_info; struct inode *root; int err; - c = alloc_ubifs_info(ubi); - if (!c) - return -ENOMEM; - c->vfs_sb = sb; /* Re-open the UBI device in read-write mode */ c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READWRITE); if (IS_ERR(c->ubi)) { err = PTR_ERR(c->ubi); - goto out_free; + goto out; } /* @@ -2100,24 +2094,29 @@ out_bdi: bdi_destroy(&c->bdi); out_close: ubi_close_volume(c->ubi); -out_free: - kfree(c); +out: return err; } static int sb_test(struct super_block *sb, void *data) { - dev_t *dev = data; + struct ubifs_info *c1 = data; struct ubifs_info *c = sb->s_fs_info; - return c->vi.cdev == *dev; + return c->vi.cdev == c1->vi.cdev; +} + +static int sb_set(struct super_block *sb, void *data) +{ + sb->s_fs_info = data; + return set_anon_super(sb, NULL); } static struct dentry *ubifs_mount(struct file_system_type *fs_type, int flags, const char *name, void *data) { struct ubi_volume_desc *ubi; - struct ubi_volume_info vi; + struct ubifs_info *c; struct super_block *sb; int err; @@ -2134,19 +2133,24 @@ static struct dentry *ubifs_mount(struct file_system_type *fs_type, int flags, name, (int)PTR_ERR(ubi)); return ERR_CAST(ubi); } - ubi_get_volume_info(ubi, &vi); - dbg_gen("opened ubi%d_%d", vi.ubi_num, vi.vol_id); + c = alloc_ubifs_info(ubi); + if (!c) { + err = -ENOMEM; + goto out_close; + } + + dbg_gen("opened ubi%d_%d", c->vi.ubi_num, c->vi.vol_id); - sb = sget(fs_type, &sb_test, &set_anon_super, &vi.cdev); + sb = sget(fs_type, sb_test, sb_set, c); if (IS_ERR(sb)) { err = PTR_ERR(sb); - goto out_close; + kfree(c); } if (sb->s_root) { struct ubifs_info *c1 = sb->s_fs_info; - + kfree(c); /* A new mount point for already mounted UBIFS */ dbg_gen("this ubi volume is already mounted"); if (!!(flags & MS_RDONLY) != c1->ro_mount) { @@ -2155,11 +2159,6 @@ static struct dentry *ubifs_mount(struct file_system_type *fs_type, int flags, } } else { sb->s_flags = flags; - /* - * Pass 'ubi' to 'fill_super()' in sb->s_fs_info where it is - * replaced by 'c'. - */ - sb->s_fs_info = ubi; err = ubifs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0); if (err) goto out_deact; @@ -2179,11 +2178,18 @@ out_close: return ERR_PTR(err); } +static void kill_ubifs_super(struct super_block *s) +{ + struct ubifs_info *c = s->s_fs_info; + kill_anon_super(s); + kfree(c); +} + static struct file_system_type ubifs_fs_type = { .name = "ubifs", .owner = THIS_MODULE, .mount = ubifs_mount, - .kill_sb = kill_anon_super, + .kill_sb = kill_ubifs_super, }; /* -- 2.20.1