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Message-ID: <ZrLt9HIxV9QiZotn@xpf.sh.intel.com>
Date: Wed, 7 Aug 2024 11:45:56 +0800
From: Pengfei Xu <pengfei.xu@...el.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-mm@...ck.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, Vlastimil
Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>, Alexander Viro
<viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara
<jack@...e.cz>, Eric Biederman <ebiederm@...ssion.com>, Kees Cook
<kees@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, SeongJae Park
<sj@...nel.org>, Shuah Khan <shuah@...nel.org>, Brendan Higgins
<brendanhiggins@...gle.com>, David Gow <davidgow@...gle.com>, Rae Moar
<rmoar@...gle.com>, <syzkaller-bugs@...glegroups.com>
Subject: Re: [PATCH v4 1/7] userfaultfd: move core VMA manipulation logic to
mm/userfaultfd.c
Hi Lorenzo Stoakes,
Greetings!
I used syzkaller and found
KASAN: slab-use-after-free Read in userfaultfd_set_ctx in next-20240805.
Bisected the first bad commit:
4651ba8201cf userfaultfd: move core VMA manipulation logic to mm/userfaultfd.c
All detailed info: https://github.com/xupengfe/syzkaller_logs/tree/main/240806_122723_userfaultfd_set_ctx
Syzkaller repro code: https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/repro.c
Syzkaller repro syscall steps: https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/repro.prog
Syzkaller analysis report: https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/repro.report
Kconfig(make olddefconfig): https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/kconfig_origin
Bisect info: https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/bisect_info.log
Dmesg: https://github.com/xupengfe/syzkaller_logs/blob/main/240806_122723_userfaultfd_set_ctx/d6dbc9f56c3a70e915625b6f1887882c23dc5c91_dmesg.log
bzImage: https://github.com/xupengfe/syzkaller_logs/raw/main/240806_122723_userfaultfd_set_ctx/bzImage_d6dbc9f56c3a70e915625b6f1887882c23dc5c91.tar.gz
"
[ 29.675551] ==================================================================
[ 29.676133] BUG: KASAN: slab-use-after-free in userfaultfd_set_ctx+0x31c/0x360
[ 29.676716] Read of size 8 at addr ffff888027c5f100 by task repro/1498
[ 29.677218]
[ 29.677358] CPU: 0 UID: 0 PID: 1498 Comm: repro Not tainted 6.11.0-rc2-next-20240805-d6dbc9f56c3a #1
[ 29.678053] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 29.678910] Call Trace:
[ 29.679117] <TASK>
[ 29.679296] dump_stack_lvl+0xea/0x150
[ 29.679622] print_report+0xce/0x610
[ 29.679924] ? userfaultfd_set_ctx+0x31c/0x360
[ 29.680289] ? kasan_complete_mode_report_info+0x80/0x200
[ 29.680716] ? userfaultfd_set_ctx+0x31c/0x360
[ 29.681077] kasan_report+0xcc/0x110
[ 29.681372] ? userfaultfd_set_ctx+0x31c/0x360
[ 29.681729] __asan_report_load8_noabort+0x18/0x20
[ 29.682118] userfaultfd_set_ctx+0x31c/0x360
[ 29.682465] userfaultfd_clear_vma+0x104/0x190
[ 29.682826] userfaultfd_release_all+0x294/0x4a0
[ 29.683201] ? __pfx_userfaultfd_release_all+0x10/0x10
[ 29.683615] ? __this_cpu_preempt_check+0x21/0x30
[ 29.684003] ? __pfx_userfaultfd_release+0x10/0x10
[ 29.684389] userfaultfd_release+0x112/0x1e0
[ 29.684735] ? __pfx_userfaultfd_release+0x10/0x10
[ 29.685114] ? evm_file_release+0x193/0x1f0
[ 29.685454] __fput+0x426/0xbc0
[ 29.685719] ? __sanitizer_cov_trace_const_cmp2+0x1c/0x30
[ 29.686153] __fput_sync+0x58/0x70
[ 29.686435] __x64_sys_close+0x93/0x120
[ 29.686744] x64_sys_call+0x189a/0x20d0
[ 29.687066] do_syscall_64+0x6d/0x140
[ 29.687371] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 29.687779] RIP: 0033:0x7f3b67b3f247
[ 29.688078] Code: ff e8 cd e3 01 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 c3 c9 f5 ff
[ 29.689519] RSP: 002b:00007ffd1f0ac7d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[ 29.690140] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3b67b3f247
[ 29.690717] RDX: 0000000020000100 RSI: 000000008010aa01 RDI: 0000000000000003
[ 29.691270] RBP: 00007ffd1f0ac7f0 R08: 00007ffd1f0ac7f0 R09: 00007ffd1f0ac7f0
[ 29.691822] R10: 00007ffd1f0ac7f0 R11: 0000000000000246 R12: 00007ffd1f0ac968
[ 29.692375] R13: 0000000000401bf9 R14: 0000000000403e08 R15: 00007f3b67c72000
[ 29.692939] </TASK>
[ 29.693124]
[ 29.693258] Allocated by task 1498:
[ 29.693545] kasan_save_stack+0x2c/0x60
[ 29.693875] kasan_save_track+0x18/0x40
[ 29.694205] kasan_save_alloc_info+0x3c/0x50
[ 29.694576] __kasan_slab_alloc+0x62/0x80
[ 29.694921] kmem_cache_alloc_noprof+0x114/0x370
[ 29.695319] vm_area_dup+0x2a/0x1b0
[ 29.695630] __split_vma+0x188/0x1020
[ 29.695952] vma_modify+0x1fc/0x390
[ 29.696250] userfaultfd_clear_vma+0xd4/0x190
[ 29.696609] userfaultfd_ioctl+0x3c0b/0x4560
[ 29.696964] __x64_sys_ioctl+0x1b9/0x230
[ 29.697295] x64_sys_call+0x1209/0x20d0
[ 29.697620] do_syscall_64+0x6d/0x140
[ 29.697937] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 29.698364]
[ 29.698508] Freed by task 1505:
[ 29.698779] kasan_save_stack+0x2c/0x60
[ 29.699110] kasan_save_track+0x18/0x40
[ 29.699441] kasan_save_free_info+0x3f/0x60
[ 29.699797] __kasan_slab_free+0x47/0x60
[ 29.700137] kmem_cache_free+0x2f2/0x4b0
[ 29.700471] vm_area_free_rcu_cb+0x7f/0xa0
[ 29.700819] rcu_core+0x877/0x18f0
[ 29.701123] rcu_core_si+0x12/0x20
[ 29.701421] handle_softirqs+0x1c7/0x870
[ 29.701760] __irq_exit_rcu+0xa9/0x120
[ 29.702082] irq_exit_rcu+0x12/0x30
[ 29.702386] sysvec_apic_timer_interrupt+0xa5/0xc0
[ 29.702802] asm_sysvec_apic_timer_interrupt+0x1f/0x30
[ 29.703237]
[ 29.703377] Last potentially related work creation:
[ 29.703782] kasan_save_stack+0x2c/0x60
[ 29.704114] __kasan_record_aux_stack+0x93/0xb0
[ 29.704503] kasan_record_aux_stack_noalloc+0xf/0x20
[ 29.704923] __call_rcu_common.constprop.0+0x72/0x6b0
[ 29.705349] call_rcu+0x12/0x20
[ 29.705625] vm_area_free+0x26/0x30
[ 29.705928] vma_complete+0x57e/0xf60
[ 29.706245] vma_merge+0x166b/0x3540
[ 29.706555] vma_modify+0x9f/0x390
[ 29.706853] userfaultfd_clear_vma+0xd4/0x190
[ 29.707227] userfaultfd_release_all+0x294/0x4a0
[ 29.707621] userfaultfd_release+0x112/0x1e0
[ 29.707991] __fput+0x426/0xbc0
[ 29.708267] __fput_sync+0x58/0x70
[ 29.708563] __x64_sys_close+0x93/0x120
[ 29.708891] x64_sys_call+0x189a/0x20d0
[ 29.709220] do_syscall_64+0x6d/0x140
[ 29.709538] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 29.709965]
[ 29.710105] The buggy address belongs to the object at ffff888027c5f0f0
[ 29.710105] which belongs to the cache vm_area_struct of size 176
[ 29.711130] The buggy address is located 16 bytes inside of
[ 29.711130] freed 176-byte region [ffff888027c5f0f0, ffff888027c5f1a0)
[ 29.712104]
[ 29.712245] The buggy address belongs to the physical page:
[ 29.712703] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27c5f
[ 29.713349] memcg:ffff8880198eaa01
[ 29.713639] flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)
[ 29.714173] page_type: 0xfdffffff(slab)
[ 29.714507] raw: 000fffffc0000000 ffff88800d319dc0 dead000000000122 0000000000000000
[ 29.715137] raw: 0000000000000000 0000000000110011 00000001fdffffff ffff8880198eaa01
[ 29.715765] page dumped because: kasan: bad access detected
[ 29.716220]
[ 29.716360] Memory state around the buggy address:
[ 29.716756] ffff888027c5f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 29.717349] ffff888027c5f080: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fa fb
[ 29.717940] >ffff888027c5f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 29.718521] ^
[ 29.718796] ffff888027c5f180: fb fb fb fb fc fc fc fc fc fc fc fc 00 00 00 00
[ 29.719388] ffff888027c5f200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 29.720025] ==================================================================
[ 29.720671] Disabling lock debugging due to kernel taint
"
Thanks!
---
If you don't need the following environment to reproduce the problem or if you
already have one reproduced environment, please ignore the following information.
How to reproduce:
git clone https://gitlab.com/xupengfe/repro_vm_env.git
cd repro_vm_env
tar -xvf repro_vm_env.tar.gz
cd repro_vm_env; ./start3.sh // it needs qemu-system-x86_64 and I used v7.1.0
// start3.sh will load bzImage_2241ab53cbb5cdb08a6b2d4688feb13971058f65 v6.2-rc5 kernel
// You could change the bzImage_xxx as you want
// Maybe you need to remove line "-drive if=pflash,format=raw,readonly=on,file=./OVMF_CODE.fd \" for different qemu version
You could use below command to log in, there is no password for root.
ssh -p 10023 root@...alhost
After login vm(virtual machine) successfully, you could transfer reproduced
binary to the vm by below way, and reproduce the problem in vm:
gcc -pthread -o repro repro.c
scp -P 10023 repro root@...alhost:/root/
Get the bzImage for target kernel:
Please use target kconfig and copy it to kernel_src/.config
make olddefconfig
make -jx bzImage //x should equal or less than cpu num your pc has
Fill the bzImage file into above start3.sh to load the target kernel in vm.
Tips:
If you already have qemu-system-x86_64, please ignore below info.
If you want to install qemu v7.1.0 version:
git clone https://github.com/qemu/qemu.git
cd qemu
git checkout -f v7.1.0
mkdir build
cd build
yum install -y ninja-build.x86_64
yum -y install libslirp-devel.x86_64
../configure --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-sdl --enable-usb-redir --enable-slirp
make
make install
Best Regards,
Thanks!
On 2024-07-29 at 12:50:35 +0100, Lorenzo Stoakes wrote:
> This patch forms part of a patch series intending to separate out VMA logic
> and render it testable from userspace, which requires that core
> manipulation functions be exposed in an mm/-internal header file.
>
> In order to do this, we must abstract APIs we wish to test, in this
> instance functions which ultimately invoke vma_modify().
>
> This patch therefore moves all logic which ultimately invokes vma_modify()
> to mm/userfaultfd.c, trying to transfer code at a functional granularity
> where possible.
>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> ---
> fs/userfaultfd.c | 160 +++-----------------------------
> include/linux/userfaultfd_k.h | 19 ++++
> mm/userfaultfd.c | 168 ++++++++++++++++++++++++++++++++++
> 3 files changed, 198 insertions(+), 149 deletions(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 27a3e9285fbf..b3ed7207df7e 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -104,21 +104,6 @@ bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
> return ctx->features & UFFD_FEATURE_WP_UNPOPULATED;
> }
>
> -static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
> - vm_flags_t flags)
> -{
> - const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP;
> -
> - vm_flags_reset(vma, flags);
> - /*
> - * For shared mappings, we want to enable writenotify while
> - * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply
> - * recalculate vma->vm_page_prot whenever userfaultfd-wp changes.
> - */
> - if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed)
> - vma_set_page_prot(vma);
> -}
> -
> static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
> int wake_flags, void *key)
> {
> @@ -615,22 +600,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
> spin_unlock_irq(&ctx->event_wqh.lock);
>
> if (release_new_ctx) {
> - struct vm_area_struct *vma;
> - struct mm_struct *mm = release_new_ctx->mm;
> - VMA_ITERATOR(vmi, mm, 0);
> -
> - /* the various vma->vm_userfaultfd_ctx still points to it */
> - mmap_write_lock(mm);
> - for_each_vma(vmi, vma) {
> - if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
> - vma_start_write(vma);
> - vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> - userfaultfd_set_vm_flags(vma,
> - vma->vm_flags & ~__VM_UFFD_FLAGS);
> - }
> - }
> - mmap_write_unlock(mm);
> -
> + userfaultfd_release_new(release_new_ctx);
> userfaultfd_ctx_put(release_new_ctx);
> }
>
> @@ -662,9 +632,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
> return 0;
>
> if (!(octx->features & UFFD_FEATURE_EVENT_FORK)) {
> - vma_start_write(vma);
> - vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> - userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS);
> + userfaultfd_reset_ctx(vma);
> return 0;
> }
>
> @@ -749,9 +717,7 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,
> up_write(&ctx->map_changing_lock);
> } else {
> /* Drop uffd context if remap feature not enabled */
> - vma_start_write(vma);
> - vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> - userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS);
> + userfaultfd_reset_ctx(vma);
> }
> }
>
> @@ -870,53 +836,13 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
> {
> struct userfaultfd_ctx *ctx = file->private_data;
> struct mm_struct *mm = ctx->mm;
> - struct vm_area_struct *vma, *prev;
> /* len == 0 means wake all */
> struct userfaultfd_wake_range range = { .len = 0, };
> - unsigned long new_flags;
> - VMA_ITERATOR(vmi, mm, 0);
>
> WRITE_ONCE(ctx->released, true);
>
> - if (!mmget_not_zero(mm))
> - goto wakeup;
> -
> - /*
> - * Flush page faults out of all CPUs. NOTE: all page faults
> - * must be retried without returning VM_FAULT_SIGBUS if
> - * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
> - * changes while handle_userfault released the mmap_lock. So
> - * it's critical that released is set to true (above), before
> - * taking the mmap_lock for writing.
> - */
> - mmap_write_lock(mm);
> - prev = NULL;
> - for_each_vma(vmi, vma) {
> - cond_resched();
> - BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
> - !!(vma->vm_flags & __VM_UFFD_FLAGS));
> - if (vma->vm_userfaultfd_ctx.ctx != ctx) {
> - prev = vma;
> - continue;
> - }
> - /* Reset ptes for the whole vma range if wr-protected */
> - if (userfaultfd_wp(vma))
> - uffd_wp_range(vma, vma->vm_start,
> - vma->vm_end - vma->vm_start, false);
> - new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS;
> - vma = vma_modify_flags_uffd(&vmi, prev, vma, vma->vm_start,
> - vma->vm_end, new_flags,
> - NULL_VM_UFFD_CTX);
> -
> - vma_start_write(vma);
> - userfaultfd_set_vm_flags(vma, new_flags);
> - vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> + userfaultfd_release_all(mm, ctx);
>
> - prev = vma;
> - }
> - mmap_write_unlock(mm);
> - mmput(mm);
> -wakeup:
> /*
> * After no new page faults can wait on this fault_*wqh, flush
> * the last page faults that may have been already waiting on
> @@ -1293,14 +1219,14 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> unsigned long arg)
> {
> struct mm_struct *mm = ctx->mm;
> - struct vm_area_struct *vma, *prev, *cur;
> + struct vm_area_struct *vma, *cur;
> int ret;
> struct uffdio_register uffdio_register;
> struct uffdio_register __user *user_uffdio_register;
> - unsigned long vm_flags, new_flags;
> + unsigned long vm_flags;
> bool found;
> bool basic_ioctls;
> - unsigned long start, end, vma_end;
> + unsigned long start, end;
> struct vma_iterator vmi;
> bool wp_async = userfaultfd_wp_async_ctx(ctx);
>
> @@ -1428,57 +1354,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> } for_each_vma_range(vmi, cur, end);
> BUG_ON(!found);
>
> - vma_iter_set(&vmi, start);
> - prev = vma_prev(&vmi);
> - if (vma->vm_start < start)
> - prev = vma;
> -
> - ret = 0;
> - for_each_vma_range(vmi, vma, end) {
> - cond_resched();
> -
> - BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async));
> - BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
> - vma->vm_userfaultfd_ctx.ctx != ctx);
> - WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
> -
> - /*
> - * Nothing to do: this vma is already registered into this
> - * userfaultfd and with the right tracking mode too.
> - */
> - if (vma->vm_userfaultfd_ctx.ctx == ctx &&
> - (vma->vm_flags & vm_flags) == vm_flags)
> - goto skip;
> -
> - if (vma->vm_start > start)
> - start = vma->vm_start;
> - vma_end = min(end, vma->vm_end);
> -
> - new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags;
> - vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end,
> - new_flags,
> - (struct vm_userfaultfd_ctx){ctx});
> - if (IS_ERR(vma)) {
> - ret = PTR_ERR(vma);
> - break;
> - }
> -
> - /*
> - * In the vma_merge() successful mprotect-like case 8:
> - * the next vma was merged into the current one and
> - * the current one has not been updated yet.
> - */
> - vma_start_write(vma);
> - userfaultfd_set_vm_flags(vma, new_flags);
> - vma->vm_userfaultfd_ctx.ctx = ctx;
> -
> - if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
> - hugetlb_unshare_all_pmds(vma);
> -
> - skip:
> - prev = vma;
> - start = vma->vm_end;
> - }
> + ret = userfaultfd_register_range(ctx, vma, vm_flags, start, end,
> + wp_async);
>
> out_unlock:
> mmap_write_unlock(mm);
> @@ -1519,7 +1396,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> struct vm_area_struct *vma, *prev, *cur;
> int ret;
> struct uffdio_range uffdio_unregister;
> - unsigned long new_flags;
> bool found;
> unsigned long start, end, vma_end;
> const void __user *buf = (void __user *)arg;
> @@ -1622,27 +1498,13 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
> }
>
> - /* Reset ptes for the whole vma range if wr-protected */
> - if (userfaultfd_wp(vma))
> - uffd_wp_range(vma, start, vma_end - start, false);
> -
> - new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS;
> - vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end,
> - new_flags, NULL_VM_UFFD_CTX);
> + vma = userfaultfd_clear_vma(&vmi, prev, vma,
> + start, vma_end);
> if (IS_ERR(vma)) {
> ret = PTR_ERR(vma);
> break;
> }
>
> - /*
> - * In the vma_merge() successful mprotect-like case 8:
> - * the next vma was merged into the current one and
> - * the current one has not been updated yet.
> - */
> - vma_start_write(vma);
> - userfaultfd_set_vm_flags(vma, new_flags);
> - vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> -
> skip:
> prev = vma;
> start = vma->vm_end;
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index a12bcf042551..9fc6ce15c499 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -267,6 +267,25 @@ extern void userfaultfd_unmap_complete(struct mm_struct *mm,
> extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma);
> extern bool userfaultfd_wp_async(struct vm_area_struct *vma);
>
> +void userfaultfd_reset_ctx(struct vm_area_struct *vma);
> +
> +struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi,
> + struct vm_area_struct *prev,
> + struct vm_area_struct *vma,
> + unsigned long start,
> + unsigned long end);
> +
> +int userfaultfd_register_range(struct userfaultfd_ctx *ctx,
> + struct vm_area_struct *vma,
> + unsigned long vm_flags,
> + unsigned long start, unsigned long end,
> + bool wp_async);
> +
> +void userfaultfd_release_new(struct userfaultfd_ctx *ctx);
> +
> +void userfaultfd_release_all(struct mm_struct *mm,
> + struct userfaultfd_ctx *ctx);
> +
> #else /* CONFIG_USERFAULTFD */
>
> /* mm helpers */
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index e54e5c8907fa..3b7715ecf292 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -1760,3 +1760,171 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
> VM_WARN_ON(!moved && !err);
> return moved ? moved : err;
> }
> +
> +static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
> + vm_flags_t flags)
> +{
> + const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP;
> +
> + vm_flags_reset(vma, flags);
> + /*
> + * For shared mappings, we want to enable writenotify while
> + * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply
> + * recalculate vma->vm_page_prot whenever userfaultfd-wp changes.
> + */
> + if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed)
> + vma_set_page_prot(vma);
> +}
> +
> +static void userfaultfd_set_ctx(struct vm_area_struct *vma,
> + struct userfaultfd_ctx *ctx,
> + unsigned long flags)
> +{
> + vma_start_write(vma);
> + vma->vm_userfaultfd_ctx = (struct vm_userfaultfd_ctx){ctx};
> + userfaultfd_set_vm_flags(vma,
> + (vma->vm_flags & ~__VM_UFFD_FLAGS) | flags);
> +}
> +
> +void userfaultfd_reset_ctx(struct vm_area_struct *vma)
> +{
> + userfaultfd_set_ctx(vma, NULL, 0);
> +}
> +
> +struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi,
> + struct vm_area_struct *prev,
> + struct vm_area_struct *vma,
> + unsigned long start,
> + unsigned long end)
> +{
> + struct vm_area_struct *ret;
> +
> + /* Reset ptes for the whole vma range if wr-protected */
> + if (userfaultfd_wp(vma))
> + uffd_wp_range(vma, start, end - start, false);
> +
> + ret = vma_modify_flags_uffd(vmi, prev, vma, start, end,
> + vma->vm_flags & ~__VM_UFFD_FLAGS,
> + NULL_VM_UFFD_CTX);
> +
> + /*
> + * In the vma_merge() successful mprotect-like case 8:
> + * the next vma was merged into the current one and
> + * the current one has not been updated yet.
> + */
> + if (!IS_ERR(ret))
> + userfaultfd_reset_ctx(vma);
> +
> + return ret;
> +}
> +
> +/* Assumes mmap write lock taken, and mm_struct pinned. */
> +int userfaultfd_register_range(struct userfaultfd_ctx *ctx,
> + struct vm_area_struct *vma,
> + unsigned long vm_flags,
> + unsigned long start, unsigned long end,
> + bool wp_async)
> +{
> + VMA_ITERATOR(vmi, ctx->mm, start);
> + struct vm_area_struct *prev = vma_prev(&vmi);
> + unsigned long vma_end;
> + unsigned long new_flags;
> +
> + if (vma->vm_start < start)
> + prev = vma;
> +
> + for_each_vma_range(vmi, vma, end) {
> + cond_resched();
> +
> + BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async));
> + BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
> + vma->vm_userfaultfd_ctx.ctx != ctx);
> + WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
> +
> + /*
> + * Nothing to do: this vma is already registered into this
> + * userfaultfd and with the right tracking mode too.
> + */
> + if (vma->vm_userfaultfd_ctx.ctx == ctx &&
> + (vma->vm_flags & vm_flags) == vm_flags)
> + goto skip;
> +
> + if (vma->vm_start > start)
> + start = vma->vm_start;
> + vma_end = min(end, vma->vm_end);
> +
> + new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags;
> + vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end,
> + new_flags,
> + (struct vm_userfaultfd_ctx){ctx});
> + if (IS_ERR(vma))
> + return PTR_ERR(vma);
> +
> + /*
> + * In the vma_merge() successful mprotect-like case 8:
> + * the next vma was merged into the current one and
> + * the current one has not been updated yet.
> + */
> + userfaultfd_set_ctx(vma, ctx, vm_flags);
> +
> + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
> + hugetlb_unshare_all_pmds(vma);
> +
> +skip:
> + prev = vma;
> + start = vma->vm_end;
> + }
> +
> + return 0;
> +}
> +
> +void userfaultfd_release_new(struct userfaultfd_ctx *ctx)
> +{
> + struct mm_struct *mm = ctx->mm;
> + struct vm_area_struct *vma;
> + VMA_ITERATOR(vmi, mm, 0);
> +
> + /* the various vma->vm_userfaultfd_ctx still points to it */
> + mmap_write_lock(mm);
> + for_each_vma(vmi, vma) {
> + if (vma->vm_userfaultfd_ctx.ctx == ctx)
> + userfaultfd_reset_ctx(vma);
> + }
> + mmap_write_unlock(mm);
> +}
> +
> +void userfaultfd_release_all(struct mm_struct *mm,
> + struct userfaultfd_ctx *ctx)
> +{
> + struct vm_area_struct *vma, *prev;
> + VMA_ITERATOR(vmi, mm, 0);
> +
> + if (!mmget_not_zero(mm))
> + return;
> +
> + /*
> + * Flush page faults out of all CPUs. NOTE: all page faults
> + * must be retried without returning VM_FAULT_SIGBUS if
> + * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
> + * changes while handle_userfault released the mmap_lock. So
> + * it's critical that released is set to true (above), before
> + * taking the mmap_lock for writing.
> + */
> + mmap_write_lock(mm);
> + prev = NULL;
> + for_each_vma(vmi, vma) {
> + cond_resched();
> + BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
> + !!(vma->vm_flags & __VM_UFFD_FLAGS));
> + if (vma->vm_userfaultfd_ctx.ctx != ctx) {
> + prev = vma;
> + continue;
> + }
> +
> + vma = userfaultfd_clear_vma(&vmi, prev, vma,
> + vma->vm_start, vma->vm_end);
> + prev = vma;
> + }
> + mmap_write_unlock(mm);
> + mmput(mm);
> +}
> --
> 2.45.2
>
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