Patch "iommufd: Call iopt_area_contig_done() under the lock" has been added to the 6.4-stable tree

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This is a note to let you know that I've just added the patch titled

    iommufd: Call iopt_area_contig_done() under the lock

to the 6.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iommufd-call-iopt_area_contig_done-under-the-lock.patch
and it can be found in the queue-6.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2dbc43213e560623d2b200e764a892e11ac2e522
Author: Jason Gunthorpe <jgg@xxxxxxxx>
Date:   Tue Jun 20 11:11:24 2023 -0300

    iommufd: Call iopt_area_contig_done() under the lock
    
    [ Upstream commit dbe245cdf5189e88d680379ed13901356628b650 ]
    
    The iter internally holds a pointer to the area and
    iopt_area_contig_done() will dereference it. The pointer is not valid
    outside the iova_rwsem.
    
    syzkaller reports:
    
      BUG: KASAN: slab-use-after-free in iommufd_access_unpin_pages+0x363/0x370
      Read of size 8 at addr ffff888022286e20 by task syz-executor669/5771
    
      CPU: 0 PID: 5771 Comm: syz-executor669 Not tainted 6.4.0-rc5-syzkaller-00313-g4c605260bc60 #0
      Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
      Call Trace:
       <TASK>
       dump_stack_lvl+0xd9/0x150
       print_address_description.constprop.0+0x2c/0x3c0
       kasan_report+0x11c/0x130
       iommufd_access_unpin_pages+0x363/0x370
       iommufd_test_access_unmap+0x24b/0x390
       iommufd_access_notify_unmap+0x24c/0x3a0
       iopt_unmap_iova_range+0x4c4/0x5f0
       iopt_unmap_all+0x27/0x50
       iommufd_ioas_unmap+0x3d0/0x490
       iommufd_fops_ioctl+0x317/0x4b0
       __x64_sys_ioctl+0x197/0x210
       do_syscall_64+0x39/0xb0
       entry_SYSCALL_64_after_hwframe+0x63/0xcd
      RIP: 0033:0x7fec1dae3b19
      Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
      RSP: 002b:00007fec1da74308 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
      RAX: ffffffffffffffda RBX: 00007fec1db6b438 RCX: 00007fec1dae3b19
      RDX: 0000000020000100 RSI: 0000000000003b86 RDI: 0000000000000003
      RBP: 00007fec1db6b430 R08: 00007fec1da74700 R09: 0000000000000000
      R10: 00007fec1da74700 R11: 0000000000000246 R12: 00007fec1db6b43c
      R13: 00007fec1db39074 R14: 6d6f692f7665642f R15: 0000000000022000
       </TASK>
    
      Allocated by task 5770:
       kasan_save_stack+0x22/0x40
       kasan_set_track+0x25/0x30
       __kasan_kmalloc+0xa2/0xb0
       iopt_alloc_area_pages+0x94/0x560
       iopt_map_user_pages+0x205/0x4e0
       iommufd_ioas_map+0x329/0x5f0
       iommufd_fops_ioctl+0x317/0x4b0
       __x64_sys_ioctl+0x197/0x210
       do_syscall_64+0x39/0xb0
       entry_SYSCALL_64_after_hwframe+0x63/0xcd
    
      Freed by task 5770:
       kasan_save_stack+0x22/0x40
       kasan_set_track+0x25/0x30
       kasan_save_free_info+0x2e/0x40
       ____kasan_slab_free+0x160/0x1c0
       slab_free_freelist_hook+0x8b/0x1c0
       __kmem_cache_free+0xaf/0x2d0
       iopt_unmap_iova_range+0x288/0x5f0
       iopt_unmap_all+0x27/0x50
       iommufd_ioas_unmap+0x3d0/0x490
       iommufd_fops_ioctl+0x317/0x4b0
       __x64_sys_ioctl+0x197/0x210
       do_syscall_64+0x39/0xb0
       entry_SYSCALL_64_after_hwframe+0x63/0xcd
    
    The parallel unmap free'd iter->area the instant the lock was released.
    
    Fixes: 51fe6141f0f6 ("iommufd: Data structure to provide IOVA to PFN mapping")
    Link: https://lore.kernel.org/r/2-v2-9a03761d445d+54-iommufd_syz2_jgg@xxxxxxxxxx
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Reported-by: syzbot+6c8d756f238a75fc3eb8@xxxxxxxxxxxxxxxxxxxxxxxxx
    Closes: https://lore.kernel.org/r/000000000000905eba05fe38e9f2@xxxxxxxxxx
    Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 4f9b2142274ce..29d05663d4d17 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -553,8 +553,8 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
 			iopt_area_iova_to_index(
 				area,
 				min(last_iova, iopt_area_last_iova(area))));
-	up_read(&iopt->iova_rwsem);
 	WARN_ON(!iopt_area_contig_done(&iter));
+	up_read(&iopt->iova_rwsem);
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_access_unpin_pages, IOMMUFD);
 



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