This patch (commit: 3a72660b07) is only slated for stable 3.12, but
should go to 3.10/11 as well, no?
On Wed, 2013-11-20 at 11:44 +0100, Jesper Nilsson wrote:
> Commit 2caacaa82a51b78fc0c800e206473874094287ed restructured
> the ipc shm to shorten critical region, but introduced a path
> where the return value could be -EPERM, even if the operation
> actually was performed.
>
> Before the commit, the err return value was reset by the return value
> from security_shm_shmctl() after the if (!ns_capable(...)) statement.
>
> Now, we still exit the if statement with err set to -EPERM,
> and in the case of SHM_UNLOCK, it is not reset at all,
> and used as the return value from shmctl.
>
> To fix this, we only set err when errors occur, leaving the
> fallthrough case alone.
>
> Signed-off-by: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Davidlohr Bueso <davidlohr@xxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Michel Lespinasse <walken@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> ipc/shm.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/ipc/shm.c b/ipc/shm.c
> index d697396..4076f9e 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -974,12 +974,15 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
> ipc_lock_object(&shp->shm_perm);
> if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
> kuid_t euid = current_euid();
> - err = -EPERM;
> if (!uid_eq(euid, shp->shm_perm.uid) &&
> - !uid_eq(euid, shp->shm_perm.cuid))
> + !uid_eq(euid, shp->shm_perm.cuid)) {
> + err = -EPERM;
> goto out_unlock0;
> - if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK))
> + }
> + if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
> + err = -EPERM;
> goto out_unlock0;
> + }
> }
>
> shm_file = shp->shm_file;
> --
> 1.8.4
>
>
> /^JN - Jesper Nilsson
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