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SubjectRe: [PATCH 1/2] ubifs: xattr: Fix some potential memory leaks while iterating entries
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在 2020/9/14 3:08, Richard Weinberger 写道:
> On Mon, Jun 1, 2020 at 11:11 AM Zhihao Cheng <chengzhihao1@huawei.com> wrote:
>>

> I agree that this needs fixing. Did you also look into getting rid of pxent?
> UBIFS uses the pxent pattern over and over and the same error got copy pasted
> a lot. :-(
>
I thought about it. I'm not sure whether it is good to drop 'pxent'.
Maybe you mean doing changes looks like following(Takes
ubifs_jnl_write_inode() for example):

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index 4a5b06f8d812..fcd5ac047b34 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -879,13 +879,19 @@ int ubifs_jnl_write_inode(struct ubifs_info *c,
const struct inode *inode)
union ubifs_key key;
struct fscrypt_name nm = {0};
struct inode *xino;
- struct ubifs_dent_node *xent, *pxent = NULL;
+ struct ubifs_dent_node *xent;

if (ui->xattr_cnt >= ubifs_xattr_max_cnt(c)) {
ubifs_err(c, "Cannot delete inode, it has too much xattrs!");
goto out_release;
}

+ fname_name(&nm) = kmalloc(UBIFS_MAX_NLEN, GFP_NOFS);
+ if (!fname_name(&nm)) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+
lowest_xent_key(c, &key, inode->i_ino);
while (1) {
xent = ubifs_tnc_next_ent(c, &key, &nm);
@@ -894,11 +900,12 @@ int ubifs_jnl_write_inode(struct ubifs_info *c,
const struct inode *inode)
if (err == -ENOENT)
break;

+ kfree(fname_name(&nm));
goto out_release;
}

- fname_name(&nm) = xent->name;
fname_len(&nm) = le16_to_cpu(xent->nlen);
+ strncpy(fname_name(&nm), xent->name, fname_len(&nm));

xino = ubifs_iget(c->vfs_sb, le64_to_cpu(xent->inum));
if (IS_ERR(xino)) {
@@ -907,6 +914,7 @@ int ubifs_jnl_write_inode(struct ubifs_info *c,
const struct inode *inode)
xent->name, err);
ubifs_ro_mode(c, err);
kfree(xent);
+ kfree(fname_name(&nm));
goto out_release;
}
ubifs_assert(c, ubifs_inode(xino)->xattr);
@@ -916,11 +924,10 @@ int ubifs_jnl_write_inode(struct ubifs_info *c,
const struct inode *inode)
ino = (void *)ino + UBIFS_INO_NODE_SZ;
iput(xino);

- kfree(pxent);
- pxent = xent;
key_read(c, &xent->key, &key);
+ kfree(xent);
}
- kfree(pxent);
+ kfree(fname_name(&nm));
}

pack_inode(c, ino, inode, 1);
The kill_xattrs process is more intuitive without the pxent. However,
the release process for the memory (stores xent->name) is similar to
'pxent'. If you think it's better than v1, I will send v2.

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