[media] Revert "[media] vb2: Push mmap_sem down to memops"

This reverts commit 48b25a3a713b90988b6882d318f7c0a6bed9aabc.

That commit caused two regressions. The first is a BUG:

Jun 14 18:42:15 test-media kernel: [  115.972299] BUG: unable to handle kernel NULL pointer dereference at 0000000000000100
Jun 14 18:42:15 test-media kernel: [  115.972307] IP: [<ffffffff810d5cd0>] __lock_acquire+0x2f0/0x2070
Jun 14 18:42:15 test-media kernel: [  115.972316] PGD 0
Jun 14 18:42:15 test-media kernel: [  115.972318] Oops: 0000 [#1] PREEMPT SMP
Jun 14 18:42:15 test-media kernel: [  115.972321] Modules linked in: vivid v4l2_dv_timings videobuf2_vmalloc videobuf2_memops videobuf2_core v4l2_common videodev media vmw_balloon vmw_vmci acpi_cpufreq processor button
Jun 14 18:42:15 test-media kernel: [  115.972333] CPU: 0 PID: 1542 Comm: v4l2-ctl Not tainted 4.1.0-rc3-test-media #1190
Jun 14 18:42:15 test-media kernel: [  115.972336] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/20/2014
Jun 14 18:42:15 test-media kernel: [  115.972337] task: ffff880220ce4200 ti: ffff88021d16c000 task.ti: ffff88021d16c000
Jun 14 18:42:15 test-media kernel: [  115.972339] RIP: 0010:[<ffffffff810d5cd0>]  [<ffffffff810d5cd0>] __lock_acquire+0x2f0/0x2070
Jun 14 18:42:15 test-media kernel: [  115.972342] RSP: 0018:ffff88021d16f9b8  EFLAGS: 00010002
Jun 14 18:42:15 test-media kernel: [  115.972343] RAX: 0000000000000046 RBX: 0000000000000292 RCX: 0000000000000001
Jun 14 18:42:15 test-media kernel: [  115.972345] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000100
Jun 14 18:42:15 test-media kernel: [  115.972346] RBP: ffff88021d16fa88 R08: 0000000000000001 R09: 0000000000000000
Jun 14 18:42:15 test-media kernel: [  115.972347] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000001
Jun 14 18:42:15 test-media kernel: [  115.972348] R13: ffff880220ce4200 R14: 0000000000000100 R15: 0000000000000000
Jun 14 18:42:15 test-media kernel: [  115.972350] FS:  00007f2441e7f740(0000) GS:ffff880236e00000(0000) knlGS:0000000000000000
Jun 14 18:42:15 test-media kernel: [  115.972351] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
Jun 14 18:42:15 test-media kernel: [  115.972353] CR2: 0000000000000100 CR3: 0000000001e0b000 CR4: 00000000001406f0
Jun 14 18:42:15 test-media kernel: [  115.972424] Stack:
Jun 14 18:42:15 test-media kernel: [  115.972427]  ffff88021d16fa98 ffffffff810d6543 0000000000000006 0000000000000246
Jun 14 18:42:15 test-media kernel: [  115.972431]  ffff88021d16fa08 ffffffff810d532d ffff880220ce4a78 ffff880200000000
Jun 14 18:42:15 test-media kernel: [  115.972433]  ffff880200000001 0000000000000000 0000000000000001 000000000093a4a0
Jun 14 18:42:15 test-media kernel: [  115.972436] Call Trace:
Jun 14 18:42:15 test-media kernel: [  115.972440]  [<ffffffff810d6543>] ? __lock_acquire+0xb63/0x2070
Jun 14 18:42:15 test-media kernel: [  115.972443]  [<ffffffff810d532d>] ? mark_held_locks+0x6d/0xa0
Jun 14 18:42:15 test-media kernel: [  115.972445]  [<ffffffff810d37a8>] ? __lock_is_held+0x58/0x80
Jun 14 18:42:15 test-media kernel: [  115.972447]  [<ffffffff810d852c>] lock_acquire+0x6c/0xa0
Jun 14 18:42:15 test-media kernel: [  115.972452]  [<ffffffffa039f1f6>] ? vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:42:15 test-media kernel: [  115.972458]  [<ffffffff819b1a92>] down_read+0x42/0x60
Jun 14 18:42:15 test-media kernel: [  115.972460]  [<ffffffffa039f1f6>] ? vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:42:15 test-media kernel: [  115.972463]  [<ffffffff819af1b1>] ? mutex_lock_nested+0x2b1/0x560
Jun 14 18:42:15 test-media kernel: [  115.972467]  [<ffffffffa038fdc5>] ? vb2_queue_release+0x25/0x40 [videobuf2_core]
Jun 14 18:42:15 test-media kernel: [  115.972469]  [<ffffffffa039f1f6>] vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:42:15 test-media kernel: [  115.972472]  [<ffffffffa038b626>] __vb2_queue_free+0x146/0x5e0 [videobuf2_core]
Jun 14 18:42:15 test-media kernel: [  115.972475]  [<ffffffffa038fdd3>] vb2_queue_release+0x33/0x40 [videobuf2_core]
Jun 14 18:42:15 test-media kernel: [  115.972478]  [<ffffffffa038fe75>] _vb2_fop_release+0x95/0xb0 [videobuf2_core]
Jun 14 18:42:15 test-media kernel: [  115.972481]  [<ffffffffa038feb9>] vb2_fop_release+0x29/0x50 [videobuf2_core]
Jun 14 18:42:15 test-media kernel: [  115.972485]  [<ffffffffa03ad372>] vivid_fop_release+0x92/0x230 [vivid]
Jun 14 18:42:15 test-media kernel: [  115.972491]  [<ffffffffa0358460>] v4l2_release+0x30/0x80 [videodev]
Jun 14 18:42:15 test-media kernel: [  115.972496]  [<ffffffff811a51d5>] __fput+0xe5/0x200
Jun 14 18:42:15 test-media kernel: [  115.972498]  [<ffffffff811a5339>] ____fput+0x9/0x10
Jun 14 18:42:15 test-media kernel: [  115.972501]  [<ffffffff810a9fa4>] task_work_run+0xc4/0xf0
Jun 14 18:42:15 test-media kernel: [  115.972504]  [<ffffffff8108c670>] do_exit+0x3a0/0xaf0
Jun 14 18:42:15 test-media kernel: [  115.972507]  [<ffffffff819b3a9b>] ? _raw_spin_unlock_irq+0x2b/0x60
Jun 14 18:42:15 test-media kernel: [  115.972509]  [<ffffffff8108e0ff>] do_group_exit+0x4f/0xe0
Jun 14 18:42:15 test-media kernel: [  115.972511]  [<ffffffff8109a170>] get_signal+0x200/0x8c0
Jun 14 18:42:15 test-media kernel: [  115.972514]  [<ffffffff819b14b5>] ? __mutex_unlock_slowpath+0xf5/0x240
Jun 14 18:42:15 test-media kernel: [  115.972518]  [<ffffffff81002593>] do_signal+0x23/0x820
Jun 14 18:42:15 test-media kernel: [  115.972521]  [<ffffffff819b1609>] ? mutex_unlock+0x9/0x10
Jun 14 18:42:15 test-media kernel: [  115.972524]  [<ffffffffa0358648>] ? v4l2_ioctl+0x78/0xf0 [videodev]
Jun 14 18:42:15 test-media kernel: [  115.972526]  [<ffffffff819b4653>] ? int_very_careful+0x5/0x46
Jun 14 18:42:15 test-media kernel: [  115.972529]  [<ffffffff810d54bd>] ? trace_hardirqs_on_caller+0x15d/0x200
Jun 14 18:42:15 test-media kernel: [  115.972531]  [<ffffffff81002de0>] do_notify_resume+0x50/0x60
Jun 14 18:42:15 test-media kernel: [  115.972533]  [<ffffffff819b46a6>] int_signal+0x12/0x17
Jun 14 18:42:15 test-media kernel: [  115.972534] Code: ca 81 31 c0 e8 7a e2 8c 00 e8 aa 1d 8d 00 0f 1f 44 00 00 31 db 48 81 c4 a8 00 00 00 89 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 66 90 <49> 81 3e 40 4e 02 82 b8 00 00 00 00 44 0f 44 e0 41 83 ff 01 0f
Jun 14 18:42:15 test-media kernel: [  115.972567] RIP  [<ffffffff810d5cd0>] __lock_acquire+0x2f0/0x2070
Jun 14 18:42:15 test-media kernel: [  115.972569]  RSP <ffff88021d16f9b8>
Jun 14 18:42:15 test-media kernel: [  115.972570] CR2: 0000000000000100
Jun 14 18:42:15 test-media kernel: [  115.972573] ---[ end trace 25595c2b8560cb57 ]---
Jun 14 18:42:15 test-media kernel: [  115.972575] Fixing recursive fault but reboot is needed!

This can be reproduced by loading the vivid driver and running:

v4l2-ctl --stream-user

and pressing Ctrl-C. You may have to try a few times, but in my experience this BUG
is triggered quite quickly.

The second is a possible deadlock:

Jun 14 18:44:07 test-media kernel: [   49.376650] ======================================================
Jun 14 18:44:07 test-media kernel: [   49.376651] [ INFO: possible circular locking dependency detected ]
Jun 14 18:44:07 test-media kernel: [   49.376653] 4.1.0-rc3-test-media #1190 Not tainted
Jun 14 18:44:07 test-media kernel: [   49.376654] -------------------------------------------------------
Jun 14 18:44:07 test-media kernel: [   49.376655] v4l2-compliance/1468 is trying to acquire lock:
Jun 14 18:44:07 test-media kernel: [   49.376657]  (&mm->mmap_sem){++++++}, at: [<ffffffffa03a81f6>] vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:44:07 test-media kernel: [   49.376665]
Jun 14 18:44:07 test-media kernel: [   49.376665] but task is already holding lock:
Jun 14 18:44:07 test-media kernel: [   49.376666]  (&q->mmap_lock){+.+...}, at: [<ffffffffa0398dc5>] vb2_queue_release+0x25/0x40 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376670]
Jun 14 18:44:07 test-media kernel: [   49.376670] which lock already depends on the new lock.
Jun 14 18:44:07 test-media kernel: [   49.376670]
Jun 14 18:44:07 test-media kernel: [   49.376671]
Jun 14 18:44:07 test-media kernel: [   49.376671] the existing dependency chain (in reverse order) is:
Jun 14 18:44:07 test-media kernel: [   49.376672]
Jun 14 18:44:07 test-media kernel: [   49.376672] -> #1 (&q->mmap_lock){+.+...}:
Jun 14 18:44:07 test-media kernel: [   49.376675]        [<ffffffff810d852c>] lock_acquire+0x6c/0xa0
Jun 14 18:44:07 test-media kernel: [   49.376682]        [<ffffffff819aef5e>] mutex_lock_nested+0x5e/0x560
Jun 14 18:44:07 test-media kernel: [   49.376689]        [<ffffffffa03934a2>] vb2_mmap+0x232/0x350 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376691]        [<ffffffffa0395a60>] vb2_fop_mmap+0x20/0x30 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376694]        [<ffffffffa0361102>] v4l2_mmap+0x52/0x90 [videodev]
Jun 14 18:44:07 test-media kernel: [   49.376698]        [<ffffffff81177e33>] mmap_region+0x3b3/0x5e0
Jun 14 18:44:07 test-media kernel: [   49.376701]        [<ffffffff81178377>] do_mmap_pgoff+0x317/0x400
Jun 14 18:44:07 test-media kernel: [   49.376703]        [<ffffffff81165320>] vm_mmap_pgoff+0x90/0xc0
Jun 14 18:44:07 test-media kernel: [   49.376708]        [<ffffffff81176867>] SyS_mmap_pgoff+0x1d7/0x280
Jun 14 18:44:07 test-media kernel: [   49.376709]        [<ffffffff81007f8d>] SyS_mmap+0x1d/0x20
Jun 14 18:44:07 test-media kernel: [   49.376714]        [<ffffffff819b44ae>] system_call_fastpath+0x12/0x76
Jun 14 18:44:07 test-media kernel: [   49.376716]
Jun 14 18:44:07 test-media kernel: [   49.376716] -> #0 (&mm->mmap_sem){++++++}:
Jun 14 18:44:07 test-media kernel: [   49.376718]        [<ffffffff810d79b3>] __lock_acquire+0x1fd3/0x2070
Jun 14 18:44:07 test-media kernel: [   49.376720]        [<ffffffff810d852c>] lock_acquire+0x6c/0xa0
Jun 14 18:44:07 test-media kernel: [   49.376721]        [<ffffffff819b1a92>] down_read+0x42/0x60
Jun 14 18:44:07 test-media kernel: [   49.376723]        [<ffffffffa03a81f6>] vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:44:07 test-media kernel: [   49.376725]        [<ffffffffa0394626>] __vb2_queue_free+0x146/0x5e0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376727]        [<ffffffffa0398dd3>] vb2_queue_release+0x33/0x40 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376729]        [<ffffffffa0398e75>] _vb2_fop_release+0x95/0xb0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376731]        [<ffffffffa0398eb9>] vb2_fop_release+0x29/0x50 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376733]        [<ffffffffa03b6372>] vivid_fop_release+0x92/0x230 [vivid]
Jun 14 18:44:07 test-media kernel: [   49.376737]        [<ffffffffa0361460>] v4l2_release+0x30/0x80 [videodev]
Jun 14 18:44:07 test-media kernel: [   49.376739]        [<ffffffff811a51d5>] __fput+0xe5/0x200
Jun 14 18:44:07 test-media kernel: [   49.376744]        [<ffffffff811a5339>] ____fput+0x9/0x10
Jun 14 18:44:07 test-media kernel: [   49.376746]        [<ffffffff810a9fa4>] task_work_run+0xc4/0xf0
Jun 14 18:44:07 test-media kernel: [   49.376749]        [<ffffffff81002dd1>] do_notify_resume+0x41/0x60
Jun 14 18:44:07 test-media kernel: [   49.376752]        [<ffffffff819b46a6>] int_signal+0x12/0x17
Jun 14 18:44:07 test-media kernel: [   49.376754]
Jun 14 18:44:07 test-media kernel: [   49.376754] other info that might help us debug this:
Jun 14 18:44:07 test-media kernel: [   49.376754]
Jun 14 18:44:07 test-media kernel: [   49.376755]  Possible unsafe locking scenario:
Jun 14 18:44:07 test-media kernel: [   49.376755]
Jun 14 18:44:07 test-media kernel: [   49.376756]        CPU0                    CPU1
Jun 14 18:44:07 test-media kernel: [   49.376757]        ----                    ----
Jun 14 18:44:07 test-media kernel: [   49.376758]   lock(&q->mmap_lock);
Jun 14 18:44:07 test-media kernel: [   49.376759]                                lock(&mm->mmap_sem);
Jun 14 18:44:07 test-media kernel: [   49.376760]                                lock(&q->mmap_lock);
Jun 14 18:44:07 test-media kernel: [   49.376761]   lock(&mm->mmap_sem);
Jun 14 18:44:07 test-media kernel: [   49.376763]
Jun 14 18:44:07 test-media kernel: [   49.376763]  *** DEADLOCK ***
Jun 14 18:44:07 test-media kernel: [   49.376763]
Jun 14 18:44:07 test-media kernel: [   49.376764] 2 locks held by v4l2-compliance/1468:
Jun 14 18:44:07 test-media kernel: [   49.376765]  #0:  (&dev->mutex#3){+.+.+.}, at: [<ffffffffa0398e0a>] _vb2_fop_release+0x2a/0xb0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376770]  #1:  (&q->mmap_lock){+.+...}, at: [<ffffffffa0398dc5>] vb2_queue_release+0x25/0x40 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376773]
Jun 14 18:44:07 test-media kernel: [   49.376773] stack backtrace:
Jun 14 18:44:07 test-media kernel: [   49.376776] CPU: 2 PID: 1468 Comm: v4l2-compliance Not tainted 4.1.0-rc3-test-media #1190
Jun 14 18:44:07 test-media kernel: [   49.376777] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/20/2014
Jun 14 18:44:07 test-media kernel: [   49.376779]  ffffffff8279e0b0 ffff88021d6f7ba8 ffffffff819a7aac 0000000000000011
Jun 14 18:44:07 test-media kernel: [   49.376781]  ffffffff8279e0b0 ffff88021d6f7bf8 ffffffff819a3964 ffff88021d6f7bd8
Jun 14 18:44:07 test-media kernel: [   49.376783]  ffff8800ac8aa100 0000000000000002 ffff8800ac8aa9a0 0000000000000002
Jun 14 18:44:07 test-media kernel: [   49.376785] Call Trace:
Jun 14 18:44:07 test-media kernel: [   49.376788]  [<ffffffff819a7aac>] dump_stack+0x4f/0x7b
Jun 14 18:44:07 test-media kernel: [   49.376792]  [<ffffffff819a3964>] print_circular_bug+0x20f/0x251
Jun 14 18:44:07 test-media kernel: [   49.376793]  [<ffffffff810d79b3>] __lock_acquire+0x1fd3/0x2070
Jun 14 18:44:07 test-media kernel: [   49.376795]  [<ffffffff810d6543>] ? __lock_acquire+0xb63/0x2070
Jun 14 18:44:07 test-media kernel: [   49.376797]  [<ffffffff810d37a8>] ? __lock_is_held+0x58/0x80
Jun 14 18:44:07 test-media kernel: [   49.376798]  [<ffffffff810d852c>] lock_acquire+0x6c/0xa0
Jun 14 18:44:07 test-media kernel: [   49.376800]  [<ffffffffa03a81f6>] ? vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:44:07 test-media kernel: [   49.376802]  [<ffffffff819b1a92>] down_read+0x42/0x60
Jun 14 18:44:07 test-media kernel: [   49.376803]  [<ffffffffa03a81f6>] ? vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:44:07 test-media kernel: [   49.376805]  [<ffffffff819af1b1>] ? mutex_lock_nested+0x2b1/0x560
Jun 14 18:44:07 test-media kernel: [   49.376807]  [<ffffffffa0398dc5>] ? vb2_queue_release+0x25/0x40 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376808]  [<ffffffffa03a81f6>] vb2_vmalloc_put_userptr+0x36/0x110 [videobuf2_vmalloc]
Jun 14 18:44:07 test-media kernel: [   49.376810]  [<ffffffffa0398e0a>] ? _vb2_fop_release+0x2a/0xb0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376812]  [<ffffffffa0394626>] __vb2_queue_free+0x146/0x5e0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376814]  [<ffffffffa0398dd3>] vb2_queue_release+0x33/0x40 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376816]  [<ffffffffa0398e75>] _vb2_fop_release+0x95/0xb0 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376818]  [<ffffffffa0398eb9>] vb2_fop_release+0x29/0x50 [videobuf2_core]
Jun 14 18:44:07 test-media kernel: [   49.376820]  [<ffffffffa03b6372>] vivid_fop_release+0x92/0x230 [vivid]
Jun 14 18:44:07 test-media kernel: [   49.376822]  [<ffffffffa0361460>] v4l2_release+0x30/0x80 [videodev]
Jun 14 18:44:07 test-media kernel: [   49.376824]  [<ffffffff811a51d5>] __fput+0xe5/0x200
Jun 14 18:44:07 test-media kernel: [   49.376825]  [<ffffffff819b4653>] ? int_very_careful+0x5/0x46
Jun 14 18:44:07 test-media kernel: [   49.376827]  [<ffffffff811a5339>] ____fput+0x9/0x10
Jun 14 18:44:07 test-media kernel: [   49.376828]  [<ffffffff810a9fa4>] task_work_run+0xc4/0xf0
Jun 14 18:44:07 test-media kernel: [   49.376830]  [<ffffffff81002dd1>] do_notify_resume+0x41/0x60
Jun 14 18:44:07 test-media kernel: [   49.376832]  [<ffffffff819b46a6>] int_signal+0x12/0x17

This can be triggered by loading the vivid module with the module option 'no_error_inj=1'
and running 'v4l2-compliance -s5'. Again, it may take a few attempts to trigger this
but for me it happens quite quickly.

Without this patch I cannot reproduce these two issues. So reverting is the best
solution for now.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

4 files changed, 3 insertions, 18 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 1a096a62ef30..d835814a24d4 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1662,7 +1662,9 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
 		ret = __qbuf_mmap(vb, b);
 		break;
 	case V4L2_MEMORY_USERPTR:
+		down_read(&current->mm->mmap_sem);
 		ret = __qbuf_userptr(vb, b);
+		up_read(&current->mm->mmap_sem);
 		break;
 	case V4L2_MEMORY_DMABUF:
 		ret = __qbuf_dmabuf(vb, b);
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 369df95af5c7..94c1e6455d36 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -532,9 +532,7 @@ static void vb2_dc_put_userptr(void *buf_priv)
 		sg_free_table(sgt);
 		kfree(sgt);
 	}
-	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
-	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }
 
@@ -618,7 +616,6 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		goto fail_buf;
 	}
 
-	down_read(&current->mm->mmap_sem);
 	/* current->mm->mmap_sem is taken by videobuf2 core */
 	vma = find_vma(current->mm, vaddr);
 	if (!vma) {
@@ -645,7 +642,6 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	if (ret) {
 		unsigned long pfn;
 		if (vb2_dc_get_user_pfn(start, n_pages, vma, &pfn) == 0) {
-			up_read(&current->mm->mmap_sem);
 			buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn);
 			buf->size = size;
 			kfree(pages);
@@ -655,7 +651,6 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		pr_err("failed to get user pages\n");
 		goto fail_vma;
 	}
-	up_read(&current->mm->mmap_sem);
 
 	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
 	if (!sgt) {
@@ -718,12 +713,10 @@ fail_get_user_pages:
 		while (n_pages)
 			put_page(pages[--n_pages]);
 
-	down_read(&current->mm->mmap_sem);
 fail_vma:
 	vb2_put_vma(buf->vma);
 
 fail_pages:
-	up_read(&current->mm->mmap_sem);
 	kfree(pages); /* kfree is NULL-proof */
 
 fail_buf:
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index d7bcb05c7058..7289b81bd7b7 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -264,7 +264,6 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	if (!buf->pages)
 		goto userptr_fail_alloc_pages;
 
-	down_read(&current->mm->mmap_sem);
 	vma = find_vma(current->mm, vaddr);
 	if (!vma) {
 		dprintk(1, "no vma for address %lu\n", vaddr);
@@ -303,7 +302,6 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
 					     1, /* force */
 					     buf->pages,
 					     NULL);
-	up_read(&current->mm->mmap_sem);
 
 	if (num_pages_from_user != buf->num_pages)
 		goto userptr_fail_get_user_pages;
@@ -333,10 +331,8 @@ userptr_fail_get_user_pages:
 	if (!vma_is_io(buf->vma))
 		while (--num_pages_from_user >= 0)
 			put_page(buf->pages[num_pages_from_user]);
-	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
 userptr_fail_find_vma:
-	up_read(&current->mm->mmap_sem);
 	kfree(buf->pages);
 userptr_fail_alloc_pages:
 	kfree(buf);
@@ -370,9 +366,7 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
 			put_page(buf->pages[i]);
 	}
 	kfree(buf->pages);
-	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
-	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }
 
diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index f6656fefc035..2fe4c27f524a 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
@@ -89,7 +89,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
 
-	down_read(&current->mm->mmap_sem);
+
 	vma = find_vma(current->mm, vaddr);
 	if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
 		if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
@@ -121,7 +121,6 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		if (!buf->vaddr)
 			goto fail_get_user_pages;
 	}
-	up_read(&current->mm->mmap_sem);
 
 	buf->vaddr += offset;
 	return buf;
@@ -134,7 +133,6 @@ fail_get_user_pages:
 	kfree(buf->pages);
 
 fail_pages_array_alloc:
-	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 
 	return NULL;
@@ -146,7 +144,6 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
 	unsigned long vaddr = (unsigned long)buf->vaddr & PAGE_MASK;
 	unsigned int i;
 
-	down_read(&current->mm->mmap_sem);
 	if (buf->pages) {
 		if (vaddr)
 			vm_unmap_ram((void *)vaddr, buf->n_pages);
@@ -160,7 +157,6 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
 		vb2_put_vma(buf->vma);
 		iounmap((__force void __iomem *)buf->vaddr);
 	}
-	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }