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| author | Hugh Dickins <hugh.dickins@tiscali.co.uk> | 2009-08-24 16:30:28 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-08-24 12:53:01 -0700 |
| commit | 353d5c30c666580347515da609dd74a2b8e9b828 (patch) | |
| tree | 03cf3b5c0bc2ce08a12af303b141503ad833178f /ipc/shm.c | |
| parent | 0257a0c0c1997aac28420e784b3ef8f3ce17f093 (diff) | |
| download | linux-353d5c30c666580347515da609dd74a2b8e9b828.tar.bz2 | |
mm: fix hugetlb bug due to user_shm_unlock call
2.6.30's commit 8a0bdec194c21c8fdef840989d0d7b742bb5d4bc removed
user_shm_lock() calls in hugetlb_file_setup() but left the
user_shm_unlock call in shm_destroy().
In detail:
Assume that can_do_hugetlb_shm() returns true and hence user_shm_lock()
is not called in hugetlb_file_setup(). However, user_shm_unlock() is
called in any case in shm_destroy() and in the following
atomic_dec_and_lock(&up->__count) in free_uid() is executed and if
up->__count gets zero, also cleanup_user_struct() is scheduled.
Note that sched_destroy_user() is empty if CONFIG_USER_SCHED is not set.
However, the ref counter up->__count gets unexpectedly non-positive and
the corresponding structs are freed even though there are live
references to them, resulting in a kernel oops after a lots of
shmget(SHM_HUGETLB)/shmctl(IPC_RMID) cycles and CONFIG_USER_SCHED set.
Hugh changed Stefan's suggested patch: can_do_hugetlb_shm() at the
time of shm_destroy() may give a different answer from at the time
of hugetlb_file_setup(). And fixed newseg()'s no_id error path,
which has missed user_shm_unlock() ever since it came in 2.6.9.
Reported-by: Stefan Huber <shuber2@gmail.com>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Tested-by: Stefan Huber <shuber2@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/shm.c')
| -rw-r--r-- | ipc/shm.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index 15dd238e5338..1bc4701ef4f0 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -174,7 +174,7 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp) shm_unlock(shp); if (!is_file_hugepages(shp->shm_file)) shmem_lock(shp->shm_file, 0, shp->mlock_user); - else + else if (shp->mlock_user) user_shm_unlock(shp->shm_file->f_path.dentry->d_inode->i_size, shp->mlock_user); fput (shp->shm_file); @@ -369,8 +369,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) /* hugetlb_file_setup applies strict accounting */ if (shmflg & SHM_NORESERVE) acctflag = VM_NORESERVE; - file = hugetlb_file_setup(name, size, acctflag); - shp->mlock_user = current_user(); + file = hugetlb_file_setup(name, size, acctflag, + &shp->mlock_user); } else { /* * Do not allow no accounting for OVERCOMMIT_NEVER, even @@ -410,6 +410,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) return error; no_id: + if (shp->mlock_user) /* shmflg & SHM_HUGETLB case */ + user_shm_unlock(size, shp->mlock_user); fput(file); no_file: security_shm_free(shp); |