Re: [PATCH] shmem: fix __shmem_file_setup error path leaks

Hillf Danton
2017-03-28T03:54:55Z

On March 28, 2017 1:06 AM Vito Caputo wrote:
>
> The existing path and memory cleanups appear to be in reverse order, and
> there's no iput() potentially leaking the inode in the last two error gotos.
>
> Also make put_memory shmem_unacct_size() conditional on !inode since if we
> entered cleanup at put_inode, shmem_evict_inode() occurs via
> iput()->iput_final(), which performs the shmem_unacct_size() for us.
>
> Signed-off-by: Vito Caputo <vcaputo@pengaru.com>
> ---
>
> This caught my eye while looking through the memfd_create() implementation.
> Included patch was compile tested only...
>
> mm/shmem.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index e67d6ba..a1a84eaf 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -4134,7 +4134,7 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
> unsigned long flags, unsigned int i_flags)
> {
> struct file *res;
> - struct inode *inode;
> + struct inode *inode = NULL;
> struct path path;
> struct super_block *sb;
> struct qstr this;
> @@ -4162,7 +4162,7 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
> res = ERR_PTR(-ENOSPC);
> inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
> if (!inode)
> - goto put_memory;
> + goto put_path;
>
> inode->i_flags |= i_flags;
> d_instantiate(path.dentry, inode);

After this routine, the inode is in use of the dcache, as its comment says.

> @@ -4170,19 +4170,22 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
> clear_nlink(inode); /* It is unlinked */
> res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
> if (IS_ERR(res))
> - goto put_path;
> + goto put_inode;
>
> res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
> &shmem_file_operations);
> if (IS_ERR(res))
> - goto put_path;
> + goto put_inode;
>
> return res;
>
> -put_memory:
> - shmem_unacct_size(flags, size);
> +put_inode:
> + iput(inode);
> put_path:
> path_put(&path);
> +put_memory:
> + if (!inode)
> + shmem_unacct_size(flags, size);
> return res;
> }
>
> --
> 2.1.4