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SubjectRe: [PATCH BUGFIX -rc6] Smackfs: remove redundant lock, fix open(,O_RDWR)

--- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:

> Hi all,
>
> Older smackfs was parsing MAC rules by characters, thus a need of
> locking write sessions on open() was needed. This lock is no longer
> useful now since each rule is handled by a single write() call.
>
> This is also a bugfix since seq_open() was not called if an open()
> O_RDWR flag was given, leading to a seq_read() without an initialized
> seq_file, thus an Oops.
>
> Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
> Reported-by: Jonathan Corbet <corbet@lwn.net>

Acked-by: Casey Schaufler <casey@schaufler-ca.com>

> --
>
> security/smack/smackfs.c | 35 ++---------------------------------
> 1 file changed, 2 insertions(+), 33 deletions(-)
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index afe7c9b..cfae8af 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -74,11 +74,6 @@ struct smk_list_entry *smack_list;
> #define SEQ_READ_FINISHED 1
>
> /*
> - * Disable concurrent writing open() operations
> - */
> -static struct semaphore smack_write_sem;
> -
> -/*
> * Values for parsing cipso rules
> * SMK_DIGITLEN: Length of a digit field in a rule.
> * SMK_CIPSOMIN: Minimum possible cipso rule length.
> @@ -168,32 +163,7 @@ static struct seq_operations load_seq_ops = {
> */
> static int smk_open_load(struct inode *inode, struct file *file)
> {
> - if ((file->f_flags & O_ACCMODE) == O_RDONLY)
> - return seq_open(file, &load_seq_ops);
> -
> - if (down_interruptible(&smack_write_sem))
> - return -ERESTARTSYS;
> -
> - return 0;
> -}
> -
> -/**
> - * smk_release_load - release() for /smack/load
> - * @inode: inode structure representing file
> - * @file: "load" file pointer
> - *
> - * For a reading session, use the seq_file release
> - * implementation.
> - * Otherwise, we are at the end of a writing session so
> - * clean everything up.
> - */
> -static int smk_release_load(struct inode *inode, struct file *file)
> -{
> - if ((file->f_flags & O_ACCMODE) == O_RDONLY)
> - return seq_release(inode, file);
> -
> - up(&smack_write_sem);
> - return 0;
> + return seq_open(file, &load_seq_ops);
> }
>
> /**
> @@ -341,7 +311,7 @@ static const struct file_operations smk_load_ops = {
> .read = seq_read,
> .llseek = seq_lseek,
> .write = smk_write_load,
> - .release = smk_release_load,
> + .release = seq_release,
> };
>
> /**
> @@ -1011,7 +981,6 @@ static int __init init_smk_fs(void)
> }
> }
>
> - sema_init(&smack_write_sem, 1);
> smk_cipso_doi();
> smk_unlbl_ambient(NULL);
>
> Regards,
>
> --
>
> "Better to light a candle, than curse the darkness"
>
> Ahmed S. Darwish
> Homepage: http://darwish.07.googlepages.com
> Blog: http://darwish-07.blogspot.com
>
>
>


Casey Schaufler
casey@schaufler-ca.com


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