Re: [PATCH] mm/vmalloc: Move free_vm_area(area) from the __vmalloc_area_node function to the __vmalloc_node_range_noprof function

From: Lai, Yi
Date: Thu Mar 13 2025 - 04:49:17 EST

On Mon, Mar 03, 2025 at 09:57:02AM +0800, Liu Ye wrote:
> Moved free_vm_area from the __vmalloc_area_node function to the
> __vmalloc_node_range_noprof function so that allocation and freeing
> of the area can be paired in one function for better readability.
>
> Signed-off-by: Liu Ye <liuye@xxxxxxxxxx>
> ---
> mm/vmalloc.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a6e7acebe9ad..dc658d4af181 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3651,7 +3651,6 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> warn_alloc(gfp_mask, NULL,
> "vmalloc error: size %lu, failed to allocated page array size %lu",
> nr_small_pages * PAGE_SIZE, array_size);
> - free_vm_area(area);
> return NULL;
> }
>
> @@ -3844,8 +3843,10 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,
>
> /* Allocate physical pages and map them into vmalloc space. */
> ret = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
> - if (!ret)
> + if (!ret) {
> + free_vm_area(area);
> goto fail;
> + }
>
> /*
> * Mark the pages as accessible, now that they are mapped.
> --
> 2.25.1
>
Hi Liu Yue,

Greetings!

I used Syzkaller and found that there is KASAN: slab-use-after-free Read in iommufd_test in linux-next tag - next-20250311.

After bisection and the first bad commit is:
"
35388cb1e37e mm/vmalloc: move free_vm_area(area) from the __vmalloc_area_node function to the __vmalloc_node_range_noprof function
"

All detailed into can be found at:
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test
Syzkaller repro code:
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test/repro.c
Syzkaller repro syscall steps:
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test/repro.prog
Syzkaller report:
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test/repro.report
Kconfig(make olddefconfig):
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test/kconfig_origin
Bisect info:
https://github.com/laifryiee/syzkaller_logs/tree/main/250312_233425_iommufd_test/bisect_info.log
bzImage:
https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/250312_233425_iommufd_test/bzImage_eea255893718268e1ab852fb52f70c613d109b99
Issue dmesg:
https://github.com/laifryiee/syzkaller_logs/blob/main/250312_233425_iommufd_test/eea255893718268e1ab852fb52f70c613d109b99_dmesg.log

"
[ 22.060519] ? __vmalloc_node_range_noprof+0x1344/0x1420
[ 22.060529] __asan_report_load8_noabort+0x18/0x20
[ 22.060540] __vmalloc_node_range_noprof+0x1344/0x1420
[ 22.060552] ? iommufd_test+0x2d8/0x4b00
[ 22.060565] ? __pfx___vmalloc_node_range_noprof+0x10/0x10
[ 22.060575] ? debug_smp_processor_id+0x20/0x30
[ 22.060588] __kvmalloc_node_noprof+0x2a9/0x6a0
[ 22.060596] ? iommufd_test+0x2d8/0x4b00
[ 22.060603] ? __fget_files+0x204/0x3b0
[ 22.060613] ? iommufd_test+0x2d8/0x4b00
[ 22.060623] iommufd_test+0x2d8/0x4b00
[ 22.060629] ? iommufd_test+0x2d8/0x4b00
[ 22.060637] ? __this_cpu_preempt_check+0x21/0x30
[ 22.060650] ? __pfx_iommufd_test+0x10/0x10
[ 22.060661] ? __might_fault+0xf1/0x1b0
[ 22.060672] ? __sanitizer_cov_trace_const_cmp8+0x1c/0x30
[ 22.060683] iommufd_fops_ioctl+0x38e/0x520
[ 22.060693] ? __pfx_iommufd_fops_ioctl+0x10/0x10
[ 22.060704] ? __this_cpu_preempt_check+0x21/0x30
[ 22.060713] ? seqcount_lockdep_reader_access.constprop.0+0xb4/0xd0
[ 22.060723] ? lockdep_hardirqs_on+0x89/0x110
[ 22.060734] ? ktime_get_coarse_real_ts64+0xb6/0x100
[ 22.060745] ? __pfx_iommufd_fops_ioctl+0x10/0x10
[ 22.060754] __x64_sys_ioctl+0x1ba/0x220
[ 22.060764] x64_sys_call+0x1233/0x2150
[ 22.060771] do_syscall_64+0x6d/0x140
[ 22.060780] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 22.060787] RIP: 0033:0x7f60b7c3ee5d
[ 22.060793] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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 8b 0d 93 af 1b 00 f7 d8 64 89 01 48
[ 22.060800] RSP: 002b:00007ffe0d196758 EFLAGS: 00000213 ORIG_RAX: 0000000000000010
[ 22.060807] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f60b7c3ee5d
[ 22.060811] RDX: 0000000020000440 RSI: 0000000000003ba0 RDI: 0000000000000003
[ 22.060815] RBP: 00007ffe0d196770 R08: 00007ffe0d196770 R09: 00007ffe0d196770
[ 22.060820] R10: 00007ffe0d196770 R11: 0000000000000213 R12: 00007ffe0d1968c8
[ 22.060824] R13: 000000000040188f R14: 0000000000403e08 R15: 00007f60b800d000
[ 22.060835] </TASK>
[ 22.060840]
[ 22.072913] Allocated by task 1316:
[ 22.073094] kasan_save_stack+0x2c/0x60
[ 22.073298] kasan_save_track+0x18/0x40
[ 22.073499] kasan_save_alloc_info+0x3c/0x50
[ 22.073723] __kasan_kmalloc+0x88/0xa0
[ 22.073926] __kmalloc_cache_node_noprof+0x1d0/0x470
[ 22.074179] __get_vm_area_node+0xf7/0x260
[ 22.074391] __vmalloc_node_range_noprof+0x25c/0x1420
[ 22.074650] __kvmalloc_node_noprof+0x2a9/0x6a0
[ 22.074888] iommufd_test+0x2d8/0x4b00
[ 22.075085] iommufd_fops_ioctl+0x38e/0x520
[ 22.075308] __x64_sys_ioctl+0x1ba/0x220
[ 22.075517] x64_sys_call+0x1233/0x2150
[ 22.075719] do_syscall_64+0x6d/0x140
[ 22.075917] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 22.076171]
[ 22.076261] Freed by task 1316:
[ 22.076428] kasan_save_stack+0x2c/0x60
[ 22.076628] kasan_save_track+0x18/0x40
[ 22.076833] kasan_save_free_info+0x3f/0x60
[ 22.077054] __kasan_slab_free+0x3d/0x60
[ 22.077258] kfree+0x28d/0x440
[ 22.077423] vfree+0x2ce/0x910
[ 22.077590] __vmalloc_node_range_noprof+0xeca/0x1420
[ 22.077854] __kvmalloc_node_noprof+0x2a9/0x6a0
[ 22.078094] iommufd_test+0x2d8/0x4b00
[ 22.078293] iommufd_fops_ioctl+0x38e/0x520
[ 22.078512] __x64_sys_ioctl+0x1ba/0x220
[ 22.078724] x64_sys_call+0x1233/0x2150
[ 22.078931] do_syscall_64+0x6d/0x140
[ 22.079128] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 22.079388]
[ 22.079478] The buggy address belongs to the object at ffff88804f5ce500
[ 22.079478] which belongs to the cache kmalloc-64 of size 64
[ 22.080073] The buggy address is located 8 bytes inside of
[ 22.080073] freed 64-byte region [ffff88804f5ce500, ffff88804f5ce540)
[ 22.080655]
[ 22.080744] The buggy address belongs to the physical page:
[ 22.081024] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f5ce
[ 22.081415] flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)
[ 22.081742] page_type: f5(slab)
[ 22.081917] raw: 000fffffc0000000 ffff88800d4418c0 dead000000000122 0000000000000000
[ 22.082297] raw: 0000000000000000 0000000000200020 00000000f5000000 0000000000000000
[ 22.082678] page dumped because: kasan: bad access detected
[ 22.082956]
[ 22.083045] Memory state around the buggy address:
[ 22.083287] ffff88804f5ce400: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 22.083646] ffff88804f5ce480: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 22.084004] >ffff88804f5ce500: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 22.084361] ^
[ 22.084542] ffff88804f5ce580: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 22.084903] ffff88804f5ce600: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 22.085263] ==================================================================
[ 22.085708] Disabling lock debugging due to kernel taint
[ 22.087471] ------------[ cut here ]------------
[ 22.087732] Trying to vfree() bad address (000000006b1be3e6)
[ 22.088039] WARNING: CPU: 1 PID: 1317 at mm/vmalloc.c:3231 remove_vm_area+0x1c2/0x220
[ 22.088421] Modules linked in:
[ 22.088590] CPU: 1 UID: 0 PID: 1317 Comm: repro Tainted: G B 6.14.0-rc6-next-20250311-eea255893718 #1
[ 22.089126] Tainted: [B]=BAD_PAGE
[ 22.089308] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 22.089869] RIP: 0010:remove_vm_area+0x1c2/0x220
[ 22.090112] Code: c3 cc cc cc cc e8 7e e2 a4 ff 49 81 ee 00 10 00 00 e9 51 ff ff ff e8 6d e2 a4 ff 4c 89 e6 48 c7 c7 a0 eb fa 85 e8 ce 71 63 ff <0f> 0b 45 31 ed eb bb 45 31 ed eb b6 e8 ed d2 0f 00 e9 10 ff ff ff
[ 22.090996] ------------[ cut here ]------------
[ 22.091042] RSP: 0018:ffff888022b77978 EFLAGS: 00010292
[ 22.091274] Trying to vfree() bad address (00000000e905f2d4)
"

Hope this cound be insightful to you.

Regards,
Yi Lai

---

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@localhost

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@localhost:/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