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Always increment/decrement ucount->count under the ucounts_lock. The
increments are there already and moving the decrements there means the
locking logic of the code is simpler. This simplification in the
locking logic fixes a race between put_ucounts and get_ucounts that
could result in a use-after-free because the count could go zero then
be found by get_ucounts and then be freed by put_ucounts.
A bug presumably this one was found by a combination of syzkaller and
KASAN. JongWhan Kim reported the syzkaller failure and Dmitry Vyukov
spotted the race in the code.
Cc: stable@vger.kernel.org
Fixes: f6b2db1a3e8d ("userns: Make the count of user namespaces per user")
Reported-by: JongHwan Kim <zzoru007@gmail.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Add #include <linux/cred.h> dependencies to all .c files rely on sched.h
doing that for them.
Note that even if the count where we need to add extra headers seems high,
it's still a net win, because <linux/sched.h> is included in over
2,200 files ...
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace updates from Eric Biederman:
"There is a lot here. A lot of these changes result in subtle user
visible differences in kernel behavior. I don't expect anything will
care but I will revert/fix things immediately if any regressions show
up.
From Seth Forshee there is a continuation of the work to make the vfs
ready for unpriviled mounts. We had thought the previous changes
prevented the creation of files outside of s_user_ns of a filesystem,
but it turns we missed the O_CREAT path. Ooops.
Pavel Tikhomirov and Oleg Nesterov worked together to fix a long
standing bug in the implemenation of PR_SET_CHILD_SUBREAPER where only
children that are forked after the prctl are considered and not
children forked before the prctl. The only known user of this prctl
systemd forks all children after the prctl. So no userspace
regressions will occur. Holding earlier forked children to the same
rules as later forked children creates a semantic that is sane enough
to allow checkpoing of processes that use this feature.
There is a long delayed change by Nikolay Borisov to limit inotify
instances inside a user namespace.
Michael Kerrisk extends the API for files used to maniuplate
namespaces with two new trivial ioctls to allow discovery of the
hierachy and properties of namespaces.
Konstantin Khlebnikov with the help of Al Viro adds code that when a
network namespace exits purges it's sysctl entries from the dcache. As
in some circumstances this could use a lot of memory.
Vivek Goyal fixed a bug with stacked filesystems where the permissions
on the wrong inode were being checked.
I continue previous work on ptracing across exec. Allowing a file to
be setuid across exec while being ptraced if the tracer has enough
credentials in the user namespace, and if the process has CAP_SETUID
in it's own namespace. Proc files for setuid or otherwise undumpable
executables are now owned by the root in the user namespace of their
mm. Allowing debugging of setuid applications in containers to work
better.
A bug I introduced with permission checking and automount is now
fixed. The big change is to mark the mounts that the kernel initiates
as a result of an automount. This allows the permission checks in sget
to be safely suppressed for this kind of mount. As the permission
check happened when the original filesystem was mounted.
Finally a special case in the mount namespace is removed preventing
unbounded chains in the mount hash table, and making the semantics
simpler which benefits CRIU.
The vfs fix along with related work in ima and evm I believe makes us
ready to finish developing and merge fully unprivileged mounts of the
fuse filesystem. The cleanups of the mount namespace makes discussing
how to fix the worst case complexity of umount. The stacked filesystem
fixes pave the way for adding multiple mappings for the filesystem
uids so that efficient and safer containers can be implemented"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
proc/sysctl: Don't grab i_lock under sysctl_lock.
vfs: Use upper filesystem inode in bprm_fill_uid()
proc/sysctl: prune stale dentries during unregistering
mnt: Tuck mounts under others instead of creating shadow/side mounts.
prctl: propagate has_child_subreaper flag to every descendant
introduce the walk_process_tree() helper
nsfs: Add an ioctl() to return owner UID of a userns
fs: Better permission checking for submounts
exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction
vfs: open() with O_CREAT should not create inodes with unknown ids
nsfs: Add an ioctl() to return the namespace type
proc: Better ownership of files for non-dumpable tasks in user namespaces
exec: Remove LSM_UNSAFE_PTRACE_CAP
exec: Test the ptracer's saved cred to see if the tracee can gain caps
exec: Don't reset euid and egid when the tracee has CAP_SETUID
inotify: Convert to using per-namespace limits
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The user_header gets caught by kmemleak with the following splat as
missing a free:
unreferenced object 0xffff99667a733d80 (size 96):
comm "swapper/0", pid 1, jiffies 4294892317 (age 62191.468s)
hex dump (first 32 bytes):
a0 b6 92 b4 ff ff ff ff 00 00 00 00 01 00 00 00 ................
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
kmemleak_alloc+0x4a/0xa0
__kmalloc+0x144/0x260
__register_sysctl_table+0x54/0x5e0
register_sysctl+0x1b/0x20
user_namespace_sysctl_init+0x17/0x34
do_one_initcall+0x52/0x1a0
kernel_init_freeable+0x173/0x200
kernel_init+0xe/0x100
ret_from_fork+0x2c/0x40
The BUG_ON()s are intended to crash so no need to clean up after
ourselves on error there. This is also a kernel/ subsys_init() we don't
need a respective exit call here as this is never modular, so just white
list it.
Link: http://lkml.kernel.org/r/20170203211404.31458-1-mcgrof@kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nikolay Borisov <n.borisov.lkml@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This patchset converts inotify to using the newly introduced
per-userns sysctl infrastructure.
Currently the inotify instances/watches are being accounted in the
user_struct structure. This means that in setups where multiple
users in unprivileged containers map to the same underlying
real user (i.e. pointing to the same user_struct) the inotify limits
are going to be shared as well, allowing one user(or application) to exhaust
all others limits.
Fix this by switching the inotify sysctls to using the
per-namespace/per-user limits. This will allow the server admin to
set sensible global limits, which can further be tuned inside every
individual user namespace. Additionally, in order to preserve the
sysctl ABI make the existing inotify instances/watches sysctls
modify the values of the initial user namespace.
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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The ucounts_lock is being used to protect various ucounts lifecycle
management functionalities. However, those services can also be invoked
when a pidns is being freed in an RCU callback (e.g. softirq context).
This can lead to deadlocks. There were already efforts trying to
prevent similar deadlocks in add7c65ca426 ("pid: fix lockdep deadlock
warning due to ucount_lock"), however they just moved the context
from hardirq to softrq. Fix this issue once and for all by explictly
making the lock disable irqs altogether.
Dmitry Vyukov <dvyukov@google.com> reported:
> I've got the following deadlock report while running syzkaller fuzzer
> on eec0d3d065bfcdf9cd5f56dd2a36b94d12d32297 of linux-next (on odroid
> device if it matters):
>
> =================================
> [ INFO: inconsistent lock state ]
> 4.10.0-rc3-next-20170112-xc2-dirty #6 Not tainted
> ---------------------------------
> inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
> swapper/2/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> (ucounts_lock){+.?...}, at: [< inline >] spin_lock
> ./include/linux/spinlock.h:302
> (ucounts_lock){+.?...}, at: [<ffff2000081678c8>]
> put_ucounts+0x60/0x138 kernel/ucount.c:162
> {SOFTIRQ-ON-W} state was registered at:
> [<ffff2000081c82d8>] mark_lock+0x220/0xb60 kernel/locking/lockdep.c:3054
> [< inline >] mark_irqflags kernel/locking/lockdep.c:2941
> [<ffff2000081c97a8>] __lock_acquire+0x388/0x3260 kernel/locking/lockdep.c:3295
> [<ffff2000081cce24>] lock_acquire+0xa4/0x138 kernel/locking/lockdep.c:3753
> [< inline >] __raw_spin_lock ./include/linux/spinlock_api_smp.h:144
> [<ffff200009798128>] _raw_spin_lock+0x90/0xd0 kernel/locking/spinlock.c:151
> [< inline >] spin_lock ./include/linux/spinlock.h:302
> [< inline >] get_ucounts kernel/ucount.c:131
> [<ffff200008167c28>] inc_ucount+0x80/0x6c8 kernel/ucount.c:189
> [< inline >] inc_mnt_namespaces fs/namespace.c:2818
> [<ffff200008481850>] alloc_mnt_ns+0x78/0x3a8 fs/namespace.c:2849
> [<ffff200008487298>] create_mnt_ns+0x28/0x200 fs/namespace.c:2959
> [< inline >] init_mount_tree fs/namespace.c:3199
> [<ffff200009bd6674>] mnt_init+0x258/0x384 fs/namespace.c:3251
> [<ffff200009bd60bc>] vfs_caches_init+0x6c/0x80 fs/dcache.c:3626
> [<ffff200009bb1114>] start_kernel+0x414/0x460 init/main.c:648
> [<ffff200009bb01e8>] __primary_switched+0x6c/0x70 arch/arm64/kernel/head.S:456
> irq event stamp: 2316924
> hardirqs last enabled at (2316924): [< inline >] rcu_do_batch
> kernel/rcu/tree.c:2911
> hardirqs last enabled at (2316924): [< inline >]
> invoke_rcu_callbacks kernel/rcu/tree.c:3182
> hardirqs last enabled at (2316924): [< inline >]
> __rcu_process_callbacks kernel/rcu/tree.c:3149
> hardirqs last enabled at (2316924): [<ffff200008210414>]
> rcu_process_callbacks+0x7a4/0xc28 kernel/rcu/tree.c:3166
> hardirqs last disabled at (2316923): [< inline >] rcu_do_batch
> kernel/rcu/tree.c:2900
> hardirqs last disabled at (2316923): [< inline >]
> invoke_rcu_callbacks kernel/rcu/tree.c:3182
> hardirqs last disabled at (2316923): [< inline >]
> __rcu_process_callbacks kernel/rcu/tree.c:3149
> hardirqs last disabled at (2316923): [<ffff20000820fe80>]
> rcu_process_callbacks+0x210/0xc28 kernel/rcu/tree.c:3166
> softirqs last enabled at (2316912): [<ffff20000811b4c4>]
> _local_bh_enable+0x4c/0x80 kernel/softirq.c:155
> softirqs last disabled at (2316913): [< inline >]
> do_softirq_own_stack ./include/linux/interrupt.h:488
> softirqs last disabled at (2316913): [< inline >]
> invoke_softirq kernel/softirq.c:371
> softirqs last disabled at (2316913): [<ffff20000811c994>]
> irq_exit+0x264/0x308 kernel/softirq.c:405
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(ucounts_lock);
> <Interrupt>
> lock(ucounts_lock);
>
> *** DEADLOCK ***
>
> 1 lock held by swapper/2/0:
> #0: (rcu_callback){......}, at: [< inline >] __rcu_reclaim
> kernel/rcu/rcu.h:108
> #0: (rcu_callback){......}, at: [< inline >] rcu_do_batch
> kernel/rcu/tree.c:2919
> #0: (rcu_callback){......}, at: [< inline >]
> invoke_rcu_callbacks kernel/rcu/tree.c:3182
> #0: (rcu_callback){......}, at: [< inline >]
> __rcu_process_callbacks kernel/rcu/tree.c:3149
> #0: (rcu_callback){......}, at: [<ffff200008210390>]
> rcu_process_callbacks+0x720/0xc28 kernel/rcu/tree.c:3166
>
> stack backtrace:
> CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.10.0-rc3-next-20170112-xc2-dirty #6
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fa60>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:500
> [<ffff20000808fec0>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:225
> [<ffff2000088a99e0>] dump_stack+0x110/0x168
> [<ffff2000082fa2b4>] print_usage_bug.part.27+0x49c/0x4bc
> kernel/locking/lockdep.c:2387
> [< inline >] print_usage_bug kernel/locking/lockdep.c:2357
> [< inline >] valid_state kernel/locking/lockdep.c:2400
> [< inline >] mark_lock_irq kernel/locking/lockdep.c:2617
> [<ffff2000081c89ec>] mark_lock+0x934/0xb60 kernel/locking/lockdep.c:3065
> [< inline >] mark_irqflags kernel/locking/lockdep.c:2923
> [<ffff2000081c9a60>] __lock_acquire+0x640/0x3260 kernel/locking/lockdep.c:3295
> [<ffff2000081cce24>] lock_acquire+0xa4/0x138 kernel/locking/lockdep.c:3753
> [< inline >] __raw_spin_lock ./include/linux/spinlock_api_smp.h:144
> [<ffff200009798128>] _raw_spin_lock+0x90/0xd0 kernel/locking/spinlock.c:151
> [< inline >] spin_lock ./include/linux/spinlock.h:302
> [<ffff2000081678c8>] put_ucounts+0x60/0x138 kernel/ucount.c:162
> [<ffff200008168364>] dec_ucount+0xf4/0x158 kernel/ucount.c:214
> [< inline >] dec_pid_namespaces kernel/pid_namespace.c:89
> [<ffff200008293dc8>] delayed_free_pidns+0x40/0xe0 kernel/pid_namespace.c:156
> [< inline >] __rcu_reclaim kernel/rcu/rcu.h:118
> [< inline >] rcu_do_batch kernel/rcu/tree.c:2919
> [< inline >] invoke_rcu_callbacks kernel/rcu/tree.c:3182
> [< inline >] __rcu_process_callbacks kernel/rcu/tree.c:3149
> [<ffff2000082103d8>] rcu_process_callbacks+0x768/0xc28 kernel/rcu/tree.c:3166
> [<ffff2000080821dc>] __do_softirq+0x324/0x6e0 kernel/softirq.c:284
> [< inline >] do_softirq_own_stack ./include/linux/interrupt.h:488
> [< inline >] invoke_softirq kernel/softirq.c:371
> [<ffff20000811c994>] irq_exit+0x264/0x308 kernel/softirq.c:405
> [<ffff2000081ecc28>] __handle_domain_irq+0xc0/0x150 kernel/irq/irqdesc.c:636
> [<ffff200008081c80>] gic_handle_irq+0x68/0xd8
> Exception stack(0xffff8000648e7dd0 to 0xffff8000648e7f00)
> 7dc0: ffff8000648d4b3c 0000000000000007
> 7de0: 0000000000000000 1ffff0000c91a967 1ffff0000c91a967 1ffff0000c91a967
> 7e00: ffff20000a4b6b68 0000000000000001 0000000000000007 0000000000000001
> 7e20: 1fffe4000149ae90 ffff200009d35000 0000000000000000 0000000000000002
> 7e40: 0000000000000000 0000000000000000 0000000002624a1a 0000000000000000
> 7e60: 0000000000000000 ffff200009cbcd88 000060006d2ed000 0000000000000140
> 7e80: ffff200009cff000 ffff200009cb6000 ffff200009cc2020 ffff200009d2159d
> 7ea0: 0000000000000000 ffff8000648d4380 0000000000000000 ffff8000648e7f00
> 7ec0: ffff20000820a478 ffff8000648e7f00 ffff20000820a47c 0000000010000145
> 7ee0: 0000000000000140 dfff200000000000 ffffffffffffffff ffff20000820a478
> [<ffff2000080837f8>] el1_irq+0xb8/0x130 arch/arm64/kernel/entry.S:486
> [< inline >] arch_local_irq_restore
> ./arch/arm64/include/asm/irqflags.h:81
> [<ffff20000820a47c>] rcu_idle_exit+0x64/0xa8 kernel/rcu/tree.c:1030
> [< inline >] cpuidle_idle_call kernel/sched/idle.c:200
> [<ffff2000081bcbfc>] do_idle+0x1dc/0x2d0 kernel/sched/idle.c:243
> [<ffff2000081bd1cc>] cpu_startup_entry+0x24/0x28 kernel/sched/idle.c:345
> [<ffff200008099f8c>] secondary_start_kernel+0x2cc/0x358
> arch/arm64/kernel/smp.c:276
> [<000000000279f1a4>] 0x279f1a4
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: add7c65ca426 ("pid: fix lockdep deadlock warning due to ucount_lock")
Fixes: f333c700c610 ("pidns: Add a limit on the number of pid namespaces")
Cc: stable@vger.kernel.org
Link: https://www.spinics.net/lists/kernel/msg2426637.html
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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v2: Fixed the very obvious lack of setting ucounts
on struct mnt_ns reported by Andrei Vagin, and the kbuild
test report.
Reported-by: Andrei Vagin <avagin@openvz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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The same kind of recursive sane default limit and policy
countrol that has been implemented for the user namespace
is desirable for the other namespaces, so generalize
the user namespace refernce count into a ucount.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Add a structure that is per user and per user ns and use it to hold
the count of user namespaces. This makes prevents one user from
creating denying service to another user by creating the maximum
number of user namespaces.
Rename the sysctl export of the maximum count from
/proc/sys/userns/max_user_namespaces to /proc/sys/user/max_user_namespaces
to reflect that the count is now per user.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Export the export the maximum number of user namespaces as
/proc/sys/userns/max_user_namespaces.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Limit per userns sysctls to only be opened for write by a holder
of CAP_SYS_RESOURCE.
Add all of the necessary boilerplate for having per user namespace
sysctls.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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