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When IPC_RMID races with other shm operations there's potential for
use-after-free of the shm object's associated file (shm_file).
Here's the race before this patch:
TASK 1 TASK 2
------ ------
shm_rmid()
ipc_lock_object()
shmctl()
shp = shm_obtain_object_check()
shm_destroy()
shum_unlock()
fput(shp->shm_file)
ipc_lock_object()
shmem_lock(shp->shm_file)
<OOPS>
The oops is caused because shm_destroy() calls fput() after dropping the
ipc_lock. fput() clears the file's f_inode, f_path.dentry, and
f_path.mnt, which causes various NULL pointer references in task 2. I
reliably see the oops in task 2 if with shmlock, shmu
This patch fixes the races by:
1) set shm_file=NULL in shm_destroy() while holding ipc_object_lock().
2) modify at risk operations to check shm_file while holding
ipc_object_lock().
Example workloads, which each trigger oops...
Workload 1:
while true; do
id=$(shmget 1 4096)
shm_rmid $id &
shmlock $id &
wait
done
The oops stack shows accessing NULL f_inode due to racing fput:
_raw_spin_lock
shmem_lock
SyS_shmctl
Workload 2:
while true; do
id=$(shmget 1 4096)
shmat $id 4096 &
shm_rmid $id &
wait
done
The oops stack is similar to workload 1 due to NULL f_inode:
touch_atime
shmem_mmap
shm_mmap
mmap_region
do_mmap_pgoff
do_shmat
SyS_shmat
Workload 3:
while true; do
id=$(shmget 1 4096)
shmlock $id
shm_rmid $id &
shmunlock $id &
wait
done
The oops stack shows second fput tripping on an NULL f_inode. The
first fput() completed via from shm_destroy(), but a racing thread did
a get_file() and queued this fput():
locks_remove_flock
__fput
____fput
task_work_run
do_notify_resume
int_signal
Fixes: c2c737a0461e ("ipc,shm: shorten critical region for shmat")
Fixes: 2caacaa82a51 ("ipc,shm: shorten critical region for shmctl")
Signed-off-by: Greg Thelen <gthelen@google.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@vger.kernel.org> # 3.10.17+ 3.11.6+
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Right now, the migration code in migrate_page_copy() uses copy_huge_page()
for hugetlbfs and thp pages:
if (PageHuge(page) || PageTransHuge(page))
copy_huge_page(newpage, page);
So, yay for code reuse. But:
void copy_huge_page(struct page *dst, struct page *src)
{
struct hstate *h = page_hstate(src);
and a non-hugetlbfs page has no page_hstate(). This works 99% of the
time because page_hstate() determines the hstate from the page order
alone. Since the page order of a THP page matches the default hugetlbfs
page order, it works.
But, if you change the default huge page size on the boot command-line
(say default_hugepagesz=1G), then we might not even *have* a 2MB hstate
so page_hstate() returns null and copy_huge_page() oopses pretty fast
since copy_huge_page() dereferences the hstate:
void copy_huge_page(struct page *dst, struct page *src)
{
struct hstate *h = page_hstate(src);
if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
...
Mel noticed that the migration code is really the only user of these
functions. This moves all the copy code over to migrate.c and makes
copy_huge_page() work for THP by checking for it explicitly.
I believe the bug was introduced in commit b32967ff101a ("mm: numa: Add
THP migration for the NUMA working set scanning fault case")
[akpm@linux-foundation.org: fix coding-style and comment text, per Naoya Horiguchi]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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checkpatch is currently confused about some complex macros and references
undefined variables $stat and $cond.
Make sure these are defined before using them.
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Gerhard Sittig <gsi@denx.de>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A race window in configfs, it starts from one dentry is UNHASHED and end
before configfs_d_iput is called. In this window, if a lookup happen,
since the original dentry was UNHASHED, so a new dentry will be
allocated, and then in configfs_attach_attr(), sd->s_dentry will be
updated to the new dentry. Then in configfs_d_iput(),
BUG_ON(sd->s_dentry != dentry) will be triggered and system panic.
sys_open: sys_close:
... fput
dput
dentry_kill
__d_drop <--- dentry unhashed here,
but sd->dentry still point
to this dentry.
lookup_real
configfs_lookup
configfs_attach_attr---> update sd->s_dentry
to new allocated dentry here.
d_kill
configfs_d_iput <--- BUG_ON(sd->s_dentry != dentry)
triggered here.
To fix it, change configfs_d_iput to not update sd->s_dentry if
sd->s_count > 2, that means there are another dentry is using the sd
beside the one that is going to be put. Use configfs_dirent_lock in
configfs_attach_attr to sync with configfs_d_iput.
With the following steps, you can reproduce the bug.
1. enable ocfs2, this will mount configfs at /sys/kernel/config and
fill configure in it.
2. run the following script.
while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done &
while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done &
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This reverts commit ea1e7ed33708c7a760419ff9ded0a6cb90586a50.
Al points out that while the commit *does* actually create a separate
slab for the page->ptl allocation, that slab is never actually used, and
the code continues to use kmalloc/kfree.
Damien Wyart points out that the original patch did have the conversion
to use kmem_cache_alloc/free, so it got lost somewhere on its way to me.
Revert the half-arsed attempt that didn't do anything. If we really do
want the special slab (remember: this is all relevant just for debug
builds, so it's not necessarily all that critical) we might as well redo
the patch fully.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill A Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Note that pmds[i] is simply uninitialized at that point...
Granted, it's very hard to hit (you need split page locks *and*
kmalloc(sizeof(spinlock_t), GFP_KERNEL) failing), but the code is
obviously bogus.
Introduced by commit 09ef4939850a ("x86: add missed
pgtable_pmd_page_ctor/dtor calls for preallocated pmds")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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I've finally tracked down why my CR signal-unwind test case still
fails on little-endian. The problem turned to be that the kernel
installs a signal trampoline in the vDSO, and provides a DWARF CFI
record for that trampoline. This CFI describes the save location
for CR:
rsave (70, 38*RSIZE + (RSIZE - CRSIZE))
which is correct for big-endian, but points to the wrong word on
little-endian. This is wrong no matter which ABI.
In addition, for the ELFv2 ABI, we should not only provide a CFI
record for register 70 (cr2), but for all CR fields separately.
Strictly speaking, I guess this would mean providing two separate
vDSO images, one for ELFv1 processes and one for ELFv2 processes (or
maybe playing some tricks with conditional DWARF expressions).
However, having CFI records for the other CR fields in ELFv1 is not
actually wrong, they just will be ignored. So it seems the simplest
fix would be just to always provide CFI for all the fields.
Signed-off-by: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Greg Thelen
Dave Hansen
Joe Perches
Junxiao Bi
Linus Torvalds
Al Viro
Ulrich Weigand