On Tue, 19 Feb 2013, Greg Thelen wrote:
> This patch fixes several mempolicy leaks in the tmpfs mount logic.
> These leaks are slow - on the order of one object leaked per mount
> attempt.
>
> Leak 1 (umount doesn't free mpol allocated in mount):
> while true; do
> mount -t tmpfs -o mpol=interleave,size=100M nodev /mnt
> umount /mnt
> done
>
> Leak 2 (errors parsing remount options will leak mpol):
> mount -t tmpfs -o size=100M nodev /mnt
> while true; do
> mount -o remount,mpol=interleave,size=x /mnt 2> /dev/null
> done
> umount /mnt
>
> Leak 3 (multiple mpol per mount leak mpol):
> while true; do
> mount -t tmpfs -o mpol=interleave,mpol=interleave,size=100M nodev /mnt
> umount /mnt
> done
>
> This patch fixes all of the above. I could have broken the patch into
> three pieces but is seemed easier to review as one.
Yes, I agree, and nicely fixed - but one doubt below. If you resolve
that, please add my Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
>
> Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
> ---
> mm/shmem.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index efd0b3a..ed2cb26 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2386,6 +2386,7 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
> bool remount)
> {
> char *this_char, *value, *rest;
> + struct mempolicy *mpol = NULL;
> uid_t uid;
> gid_t gid;
>
> @@ -2414,7 +2415,7 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
> printk(KERN_ERR
> "tmpfs: No value for mount option '%s'\n",
> this_char);
> - return 1;
> + goto error;
> }
>
> if (!strcmp(this_char,"size")) {
> @@ -2463,19 +2464,23 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
> if (!gid_valid(sbinfo->gid))
> goto bad_val;
> } else if (!strcmp(this_char,"mpol")) {
> - if (mpol_parse_str(value, &sbinfo->mpol))
> + mpol_put(mpol);
I haven't tested to check, but don't we need
mpol = NULL;
here, in case the new option turns out to be bad?
> + if (mpol_parse_str(value, &mpol))
> goto bad_val;
> } else {
> printk(KERN_ERR "tmpfs: Bad mount option %s\n",
> this_char);
> - return 1;
> + goto error;
> }
> }
> + sbinfo->mpol = mpol;
> return 0;
>
> bad_val:
> printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
> value, this_char);
> +error:
> + mpol_put(mpol);
> return 1;
>
> }
> @@ -2551,6 +2556,7 @@ static void shmem_put_super(struct super_block *sb)
> struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
>
> percpu_counter_destroy(&sbinfo->used_blocks);
> + mpol_put(sbinfo->mpol);
> kfree(sbinfo);
> sb->s_fs_info = NULL;
> }
> --
> 1.8.1.3
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