From: Jason Gunthorpe jgg@nvidia.com
[ Upstream commit 804ca14d04df09bf7924bacc5ad22a4bed80c94f ]
A concurrent unmap can trigger freeing of the area pointers while we are generating an unmapping notification for accesses.
syzkaller reports:
BUG: KASAN: slab-use-after-free in iopt_unmap_iova_range+0x5ba/0x5f0 Read of size 4 at addr ffff888075996184 by task syz-executor.2/31160
CPU: 1 PID: 31160 Comm: syz-executor.2 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 iopt_unmap_iova_range+0x5ba/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: 0033:0x7f0812c8c169 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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:00007f0813914168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0812dabf80 RCX: 00007f0812c8c169 RDX: 0000000020000100 RSI: 0000000000003b86 RDI: 0000000000000005 RBP: 00007f0812ce7ca1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0812ecfb1f R14: 00007f0813914300 R15: 0000000000022000 </TASK>
Allocated by task 31160: 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 31161: 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 buggy address belongs to the object at ffff888075996100 which belongs to the cache kmalloc-cg-192 of size 192 The buggy address is located 132 bytes inside of freed 192-byte region [ffff888075996100, ffff8880759961c0)
The buggy address belongs to the physical page: page:ffffea0001d66580 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x75996 memcg:ffff88801f1c2701 flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff) page_type: 0xffffffff() raw: 00fff00000000200 ffff88801244ddc0 dead000000000122 0000000000000000 raw: 0000000000000000 0000000080100010 00000001ffffffff ffff88801f1c2701 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 31157, tgid 31154 (syz-executor.0), ts 1984547323469, free_ts 1983933451331 post_alloc_hook+0x2db/0x350 get_page_from_freelist+0xf41/0x2c00 __alloc_pages+0x1cb/0x4a0 alloc_pages+0x1aa/0x270 allocate_slab+0x25f/0x390 ___slab_alloc+0xa91/0x1400 __slab_alloc.constprop.0+0x56/0xa0 __kmem_cache_alloc_node+0x136/0x320 kmalloc_trace+0x26/0xe0 iommufd_test+0x1328/0x2c20 iommufd_fops_ioctl+0x317/0x4b0 __x64_sys_ioctl+0x197/0x210 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x63/0xcd page last free stack trace: free_unref_page_prepare+0x62e/0xcb0 free_unref_page_list+0xe3/0xa70 release_pages+0xcd8/0x1380 tlb_batch_pages_flush+0xa8/0x1a0 tlb_finish_mmu+0x14b/0x7e0 exit_mmap+0x2b2/0x930 __mmput+0x128/0x4c0 mmput+0x60/0x70 do_exit+0x9b0/0x29b0 do_group_exit+0xd4/0x2a0 get_signal+0x2318/0x25b0 arch_do_signal_or_restart+0x79/0x5c0 exit_to_user_mode_prepare+0x11f/0x240 syscall_exit_to_user_mode+0x1d/0x50 do_syscall_64+0x46/0xb0 entry_SYSCALL_64_after_hwframe+0x63/0xcd
Precompute what is needed to call the access function and do not check the area's num_accesses again as the pointer may not be valid anymore. Use a counter instead.
Fixes: 51fe6141f0f6 ("iommufd: Data structure to provide IOVA to PFN mapping") Link: https://lore.kernel.org/r/1-v2-9a03761d445d+54-iommufd_syz2_jgg@nvidia.com Reviewed-by: Kevin Tian kevin.tian@intel.com Reported-by: syzbot+1ad12d16afca0e7d2dde@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/0000000000001d40fc05fe385332@google.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/iommufd/io_pagetable.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c index e0ae72b9e67f8..724c4c5742417 100644 --- a/drivers/iommu/iommufd/io_pagetable.c +++ b/drivers/iommu/iommufd/io_pagetable.c @@ -458,6 +458,7 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, unsigned long start, { struct iopt_area *area; unsigned long unmapped_bytes = 0; + unsigned int tries = 0; int rc = -ENOENT;
/* @@ -484,19 +485,26 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, unsigned long start, goto out_unlock_iova; }
+ if (area_first != start) + tries = 0; + /* * num_accesses writers must hold the iova_rwsem too, so we can * safely read it under the write side of the iovam_rwsem * without the pages->mutex. */ if (area->num_accesses) { + size_t length = iopt_area_length(area); + start = area_first; area->prevent_access = true; up_write(&iopt->iova_rwsem); up_read(&iopt->domains_rwsem); - iommufd_access_notify_unmap(iopt, area_first, - iopt_area_length(area)); - if (WARN_ON(READ_ONCE(area->num_accesses))) + + iommufd_access_notify_unmap(iopt, area_first, length); + /* Something is not responding to unmap requests. */ + tries++; + if (WARN_ON(tries > 100)) return -EDEADLOCK; goto again; }