[PATCH v2] ubifs: dirty_cow_znode: Fix memleak in error handling path
Zhihao Cheng
chengzhihao1 at huawei.com
Sun Feb 26 17:12:01 PST 2023
在 2023/2/15 10:25, Zhihao Cheng 写道:
Hi, Richarch,
> Following process will cause a memleak for copied up znode:
>
> dirty_cow_znode
> zn = copy_znode(c, znode);
> err = insert_old_idx(c, zbr->lnum, zbr->offs);
> if (unlikely(err))
> return ERR_PTR(err); // No one refers to zn.
>
> Fetch a reproducer in [Link].
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216705
> Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
> Signed-off-by: Zhihao Cheng <chengzhihao1 at huawei.com>
> ---
> v1: https://patchwork.ozlabs.org/project/linux-mtd/patch/20221118090236.664244-3-chengzhihao1@huawei.com/
> v1->v2: In v1, if insert_old_idx() failed, old index neither exists in
> TNC nor in old-index tree. Which means that old index node could
> be overwritten in layout_leb_in_gaps(), then ubifs image will be
> corrupted in power-cut.
> In v2, copy_znode() is splitted into 2 parts: resouce allocation
> and znode replacement, insert_old_idx() is splitted in similar
> way, so resouce cleanup could be done in error handling path
> without corrupting metadata(mem & disk).
> It's okay that old index inserting is put behind of add_idx_dirt(),
> old index is used in layout_leb_in_gaps(), so the two processes
> do not depend on each other.
> fs/ubifs/tnc.c | 137 +++++++++++++++++++++++++++++++------------------
> 1 file changed, 87 insertions(+), 50 deletions(-)
>
Just a reminder to notify that this is a v2 fix to replace original
solution (which is in next branch)
https://patchwork.ozlabs.org/project/linux-mtd/patch/20221118090236.664244-3-chengzhihao1@huawei.com/.
> diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
> index 2df56bbc6865..6b7d95b65f4b 100644
> --- a/fs/ubifs/tnc.c
> +++ b/fs/ubifs/tnc.c
> @@ -44,6 +44,33 @@ enum {
> NOT_ON_MEDIA = 3,
> };
>
> +static void do_insert_old_idx(struct ubifs_info *c,
> + struct ubifs_old_idx *old_idx)
> +{
> + struct ubifs_old_idx *o;
> + struct rb_node **p, *parent = NULL;
> +
> + p = &c->old_idx.rb_node;
> + while (*p) {
> + parent = *p;
> + o = rb_entry(parent, struct ubifs_old_idx, rb);
> + if (old_idx->lnum < o->lnum)
> + p = &(*p)->rb_left;
> + else if (old_idx->lnum > o->lnum)
> + p = &(*p)->rb_right;
> + else if (old_idx->offs < o->offs)
> + p = &(*p)->rb_left;
> + else if (old_idx->offs > o->offs)
> + p = &(*p)->rb_right;
> + else {
> + ubifs_err(c, "old idx added twice!");
> + kfree(old_idx);
> + }
> + }
> + rb_link_node(&old_idx->rb, parent, p);
> + rb_insert_color(&old_idx->rb, &c->old_idx);
> +}
> +
> /**
> * insert_old_idx - record an index node obsoleted since the last commit start.
> * @c: UBIFS file-system description object
> @@ -69,35 +96,15 @@ enum {
> */
> static int insert_old_idx(struct ubifs_info *c, int lnum, int offs)
> {
> - struct ubifs_old_idx *old_idx, *o;
> - struct rb_node **p, *parent = NULL;
> + struct ubifs_old_idx *old_idx;
>
> old_idx = kmalloc(sizeof(struct ubifs_old_idx), GFP_NOFS);
> if (unlikely(!old_idx))
> return -ENOMEM;
> old_idx->lnum = lnum;
> old_idx->offs = offs;
> + do_insert_old_idx(c, old_idx);
>
> - p = &c->old_idx.rb_node;
> - while (*p) {
> - parent = *p;
> - o = rb_entry(parent, struct ubifs_old_idx, rb);
> - if (lnum < o->lnum)
> - p = &(*p)->rb_left;
> - else if (lnum > o->lnum)
> - p = &(*p)->rb_right;
> - else if (offs < o->offs)
> - p = &(*p)->rb_left;
> - else if (offs > o->offs)
> - p = &(*p)->rb_right;
> - else {
> - ubifs_err(c, "old idx added twice!");
> - kfree(old_idx);
> - return 0;
> - }
> - }
> - rb_link_node(&old_idx->rb, parent, p);
> - rb_insert_color(&old_idx->rb, &c->old_idx);
> return 0;
> }
>
> @@ -199,23 +206,6 @@ static struct ubifs_znode *copy_znode(struct ubifs_info *c,
> __set_bit(DIRTY_ZNODE, &zn->flags);
> __clear_bit(COW_ZNODE, &zn->flags);
>
> - ubifs_assert(c, !ubifs_zn_obsolete(znode));
> - __set_bit(OBSOLETE_ZNODE, &znode->flags);
> -
> - if (znode->level != 0) {
> - int i;
> - const int n = zn->child_cnt;
> -
> - /* The children now have new parent */
> - for (i = 0; i < n; i++) {
> - struct ubifs_zbranch *zbr = &zn->zbranch[i];
> -
> - if (zbr->znode)
> - zbr->znode->parent = zn;
> - }
> - }
> -
> - atomic_long_inc(&c->dirty_zn_cnt);
> return zn;
> }
>
> @@ -233,6 +223,42 @@ static int add_idx_dirt(struct ubifs_info *c, int lnum, int dirt)
> return ubifs_add_dirt(c, lnum, dirt);
> }
>
> +/**
> + * replace_znode - replace old znode with new znode.
> + * @c: UBIFS file-system description object
> + * @new_zn: new znode
> + * @old_zn: old znode
> + * @zbr: the branch of parent znode
> + *
> + * Replace old znode with new znode in TNC.
> + */
> +static void replace_znode(struct ubifs_info *c, struct ubifs_znode *new_zn,
> + struct ubifs_znode *old_zn, struct ubifs_zbranch *zbr)
> +{
> + ubifs_assert(c, !ubifs_zn_obsolete(old_zn));
> + __set_bit(OBSOLETE_ZNODE, &old_zn->flags);
> +
> + if (old_zn->level != 0) {
> + int i;
> + const int n = new_zn->child_cnt;
> +
> + /* The children now have new parent */
> + for (i = 0; i < n; i++) {
> + struct ubifs_zbranch *child = &new_zn->zbranch[i];
> +
> + if (child->znode)
> + child->znode->parent = new_zn;
> + }
> + }
> +
> + zbr->znode = new_zn;
> + zbr->lnum = 0;
> + zbr->offs = 0;
> + zbr->len = 0;
> +
> + atomic_long_inc(&c->dirty_zn_cnt);
> +}
> +
> /**
> * dirty_cow_znode - ensure a znode is not being committed.
> * @c: UBIFS file-system description object
> @@ -265,21 +291,32 @@ static struct ubifs_znode *dirty_cow_znode(struct ubifs_info *c,
> return zn;
>
> if (zbr->len) {
> - err = insert_old_idx(c, zbr->lnum, zbr->offs);
> - if (unlikely(err))
> - return ERR_PTR(err);
> + struct ubifs_old_idx *old_idx;
> +
> + old_idx = kmalloc(sizeof(struct ubifs_old_idx), GFP_NOFS);
> + if (unlikely(!old_idx)) {
> + err = -ENOMEM;
> + goto out;
> + }
> + old_idx->lnum = zbr->lnum;
> + old_idx->offs = zbr->offs;
> +
> err = add_idx_dirt(c, zbr->lnum, zbr->len);
> - } else
> - err = 0;
> + if (err) {
> + kfree(old_idx);
> + goto out;
> + }
>
> - zbr->znode = zn;
> - zbr->lnum = 0;
> - zbr->offs = 0;
> - zbr->len = 0;
> + do_insert_old_idx(c, old_idx);
> + }
> +
> + replace_znode(c, zn, znode, zbr);
>
> - if (unlikely(err))
> - return ERR_PTR(err);
> return zn;
> +
> +out:
> + kfree(zn);
> + return ERR_PTR(err);
> }
>
> /**
>
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