linux/include
Hugh Dickins 353d5c30c6 mm: fix hugetlb bug due to user_shm_unlock call
2.6.30's commit 8a0bdec194 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>
2009-08-24 12:53:01 -07:00
..
acpi Revert "ACPICA: Remove obsolete acpi_os_validate_address interface" 2009-07-27 18:42:38 -04:00
asm-generic mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
crypto
drm drm/radeon: add GET_PARAM/INFO support for Z pipes 2009-08-21 19:10:30 +10:00
keys
linux mm: fix hugetlb bug due to user_shm_unlock call 2009-08-24 12:53:01 -07:00
math-emu
media V4L/DVB (12283): gspca - sn9c20x: New subdriver for sn9c201 and sn9c202 bridges. 2009-07-24 14:03:30 -03:00
mtd
net pkt_sched: Convert qdisc_watchdog to tasklet_hrtimer 2009-08-22 18:09:17 -07:00
pcmcia
rdma
rxrpc
scsi
sound
trace perf_counter: Zero dead bytes from ftrace raw samples size alignment 2009-08-10 16:51:19 +02:00
video
xen
Kbuild