Re: [PATCH 4/4] mm/madvise: remove redundant mmap_lock operations from process_madvise()

From: Lai, Yi
Date: Tue Feb 11 2025 - 00:30:59 EST

On Wed, Feb 05, 2025 at 10:15:17PM -0800, SeongJae Park wrote:
> Optimize redundant mmap lock operations from process_madvise() by
> directly doing the mmap locking first, and then the remaining works for
> all ranges in the loop.
>
> Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
> ---
> mm/madvise.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 31e5df75b926..5a0a1fc99d27 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1754,9 +1754,26 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter,
>
> total_len = iov_iter_count(iter);
>
> + ret = madvise_lock(mm, behavior);
> + if (ret)
> + return ret;
> +
> while (iov_iter_count(iter)) {
> - ret = do_madvise(mm, (unsigned long)iter_iov_addr(iter),
> - iter_iov_len(iter), behavior);
> + unsigned long start = (unsigned long)iter_iov_addr(iter);
> + size_t len_in = iter_iov_len(iter);
> + size_t len;
> +
> + if (!is_valid_madvise(start, len_in, behavior)) {
> + ret = -EINVAL;
> + break;
> + }
> +
> + len = PAGE_ALIGN(len_in);
> + if (start + len == start)
> + ret = 0;
> + else
> + ret = madvise_do_behavior(mm, start, len_in, len,
> + behavior);
> /*
> * An madvise operation is attempting to restart the syscall,
> * but we cannot proceed as it would not be correct to repeat
> @@ -1772,12 +1789,17 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter,
> ret = -EINTR;
> break;
> }
> +
> + /* Drop and reacquire lock to unwind race. */
> + madvise_unlock(mm, behavior);
> + madvise_lock(mm, behavior);
> continue;
> }
> if (ret < 0)
> break;
> iov_iter_advance(iter, iter_iov_len(iter));
> }
> + madvise_unlock(mm, behavior);
>
> ret = (total_len - iov_iter_count(iter)) ? : ret;
>

Hi SeongJae Park,

Greetings!

I used Syzkaller and found that there is WARNING in madvise_unlock in linux-next tag - next-20250210.

After bisection and the first bad commit is:
"
ec68fbd9e99f mm/madvise: remove redundant mmap_lock operations from process_madvise()
"

All detailed into can be found at:
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock
Syzkaller repro code:
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock/repro.c
Syzkaller repro syscall steps:
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock/repro.prog
Syzkaller report:
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock/repro.report
Kconfig(make olddefconfig):
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock/kconfig_origin
Bisect info:
https://github.com/laifryiee/syzkaller_logs/tree/main/250210_144836_madvise_unlock/bisect_info.log
bzImage:
https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/250210_144836_madvise_unlock/bzImage_df5d6180169ae06a2eac57e33b077ad6f6252440
Issue dmesg:
https://github.com/laifryiee/syzkaller_logs/blob/main/250210_144836_madvise_unlock/df5d6180169ae06a2eac57e33b077ad6f6252440_dmesg.log

"
[ 135.191347] Injecting memory failure for pfn 0x8ea0 at process virtual address 0x20e7f000
[ 135.194964] Memory failure: 0x8ea0: recovery action for reserved kernel page: Ignored
[ 135.195584] ------------[ cut here ]------------
[ 135.195863] WARNING: CPU: 1 PID: 680 at ./include/linux/rwsem.h:203 madvise_unlock+0x17e/0x1a0
[ 135.196395] Modules linked in:
[ 135.196612] CPU: 1 UID: 0 PID: 680 Comm: repro Not tainted 6.14.0-rc2-next-20250210-df5d6180169a #1
[ 135.197135] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 135.197818] RIP: 0010:madvise_unlock+0x17e/0x1a0
[ 135.198108] Code: a1 9f ff 31 f6 49 8d bc 24 e0 01 00 00 e8 fa 80 d5 03 31 ff 89 c3 89 c6 e8 9f 9b 9f ff 85 db 0f 85 1c ff ff ffe
[ 135.199154] RSP: 0018:ffff888022647e88 EFLAGS: 00010293
[ 135.199468] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81e878f1
[ 135.199876] RDX: ffff88802264a540 RSI: ffffffff81e878fe RDI: 0000000000000005
[ 135.200285] RBP: ffff888022647ea0 R08: 0000000000000001 R09: ffffed10044c8f25
[ 135.200692] R10: 0000000000000000 R11: 0000000000000001 R12: ffff888021116180
[ 135.201100] R13: ffff8880211162f0 R14: 0000000000004000 R15: ffff888021116180
[ 135.201531] FS: 00007f0327a07600(0000) GS:ffff88806c500000(0000) knlGS:0000000000000000
[ 135.201996] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 135.202329] CR2: 00007f032773e7f0 CR3: 0000000021bd4003 CR4: 0000000000770ef0
[ 135.202737] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 135.203155] DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400
[ 135.203563] PKRU: 55555554
[ 135.203731] Call Trace:
[ 135.203883] <TASK>
[ 135.204020] ? show_regs+0x6d/0x80
[ 135.204240] ? __warn+0xf3/0x390
[ 135.204447] ? report_bug+0x25e/0x4b0
[ 135.204692] ? madvise_unlock+0x17e/0x1a0
[ 135.204937] ? report_bug+0x2cb/0x4b0
[ 135.205167] ? madvise_unlock+0x17e/0x1a0
[ 135.205413] ? madvise_unlock+0x17f/0x1a0
[ 135.205706] ? handle_bug+0xf1/0x190
[ 135.206188] ? exc_invalid_op+0x3c/0x80
[ 135.206423] ? asm_exc_invalid_op+0x1f/0x30
[ 135.206678] ? madvise_unlock+0x171/0x1a0
[ 135.206919] ? madvise_unlock+0x17e/0x1a0
[ 135.207156] ? madvise_unlock+0x17e/0x1a0
[ 135.207388] ? madvise_unlock+0x17e/0x1a0
[ 135.207623] do_madvise+0x14f/0x1a0
[ 135.207836] __x64_sys_madvise+0xb2/0x120
[ 135.208067] ? syscall_trace_enter+0x14f/0x280
[ 135.208328] x64_sys_call+0x19b1/0x2150
[ 135.208552] do_syscall_64+0x6d/0x140
[ 135.208766] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 135.209050] RIP: 0033:0x7f032763ee5d
[ 135.209261] 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 8b8
[ 135.210261] RSP: 002b:00007ffcaafd26c8 EFLAGS: 00000207 ORIG_RAX: 000000000000001c
[ 135.210678] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f032763ee5d
[ 135.211069] RDX: 0000000000000064 RSI: 0000000000004000 RDI: 0000000020e7f000
[ 135.211458] RBP: 00007ffcaafd26d0 R08: 00007ffcaafd2140 R09: 00007ffcaafd2700
[ 135.211851] R10: 0000000000000000 R11: 0000000000000207 R12: 00007ffcaafd2828
[ 135.212248] R13: 00000000004016da R14: 0000000000403e08 R15: 00007f0327a4e000
[ 135.212656] </TASK>
[ 135.212794] irq event stamp: 807
[ 135.212987] hardirqs last enabled at (815): [<ffffffff81663b55>] __up_console_sem+0x95/0xb0
[ 135.213477] hardirqs last disabled at (824): [<ffffffff81663b3a>] __up_console_sem+0x7a/0xb0
[ 135.213951] softirqs last enabled at (628): [<ffffffff8148c40e>] __irq_exit_rcu+0x10e/0x170
[ 135.214426] softirqs last disabled at (623): [<ffffffff8148c40e>] __irq_exit_rcu+0x10e/0x170
[ 135.214910] ---[ end trace 0000000000000000 ]---
[ 135.215182]
[ 135.215283] =====================================
[ 135.215550] WARNING: bad unlock balance detected!
[ 135.215817] 6.14.0-rc2-next-20250210-df5d6180169a #1 Tainted: G W
[ 135.216234] -------------------------------------
[ 135.216502] repro/680 is trying to release lock (&mm->mmap_lock) at:
[ 135.216863] [<ffffffff81e87854>] madvise_unlock+0xd4/0x1a0
[ 135.217179] but there are no more locks to release!
[ 135.217457]
[ 135.217457] other info that might help us debug this:
[ 135.217819] no locks held by repro/680.
[ 135.218046]
[ 135.218046] stack backtrace:
[ 135.218296] CPU: 1 UID: 0 PID: 680 Comm: repro Tainted: G W 6.14.0-rc2-next-20250210-df5d6180169a #1
[ 135.218308] Tainted: [W]=WARN
[ 135.218310] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 135.218315] Call Trace:
[ 135.218317] <TASK>
[ 135.218320] dump_stack_lvl+0xea/0x150
[ 135.218330] ? madvise_unlock+0xd4/0x1a0
[ 135.218341] dump_stack+0x19/0x20
[ 135.218349] print_unlock_imbalance_bug+0x1b5/0x200
[ 135.218368] ? madvise_unlock+0xd4/0x1a0
[ 135.218379] lock_release+0x5bc/0x870
[ 135.218386] ? madvise_unlock+0x17f/0x1a0
[ 135.218397] ? handle_bug+0xf1/0x190
[ 135.218407] ? __pfx_lock_release+0x10/0x10
[ 135.218415] ? exc_invalid_op+0x3c/0x80
[ 135.218426] ? asm_exc_invalid_op+0x1f/0x30
[ 135.218441] up_write+0x31/0x550
[ 135.218449] ? madvise_unlock+0x17e/0x1a0
[ 135.218462] madvise_unlock+0xd4/0x1a0
[ 135.218474] do_madvise+0x14f/0x1a0
[ 135.218487] __x64_sys_madvise+0xb2/0x120
[ 135.218500] ? syscall_trace_enter+0x14f/0x280
[ 135.218511] x64_sys_call+0x19b1/0x2150
[ 135.218522] do_syscall_64+0x6d/0x140
[ 135.218531] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 135.218542] RIP: 0033:0x7f032763ee5d
[ 135.218548] 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 8b8
[ 135.218556] RSP: 002b:00007ffcaafd26c8 EFLAGS: 00000207 ORIG_RAX: 000000000000001c
[ 135.218562] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f032763ee5d
[ 135.218569] RDX: 0000000000000064 RSI: 0000000000004000 RDI: 0000000020e7f000
[ 135.218573] RBP: 00007ffcaafd26d0 R08: 00007ffcaafd2140 R09: 00007ffcaafd2700
[ 135.218578] R10: 0000000000000000 R11: 0000000000000207 R12: 00007ffcaafd2828
[ 135.218582] R13: 00000000004016da R14: 0000000000403e08 R15: 00007f0327a4e000
[ 135.218594] </TASK>
[ 135.228272] ------------[ cut here ]------------
[ 135.228541] DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magy
[ 135.229541] WARNING: CPU: 1 PID: 680 at kernel/locking/rwsem.c:1367 up_write+0x451/0x550
[ 135.229997] Modules linked in:
[ 135.230182] CPU: 1 UID: 0 PID: 680 Comm: repro Tainted: G W 6.14.0-rc2-next-20250210-df5d6180169a #1
[ 135.230758] Tainted: [W]=WARN
[ 135.230940] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 135.231565] RIP: 0010:up_write+0x451/0x550
[ 135.231806] Code: ea 03 80 3c 02 00 0f 85 d5 00 00 00 49 8b 14 24 53 4d 89 f9 4c 89 f1 48 c7 c6 40 bd eb 85 48 c7 c7 60 bc eb 858
[ 135.232814] RSP: 0018:ffff888022647e30 EFLAGS: 00010282
[ 135.233113] RAX: 0000000000000000 RBX: ffffffff85ebbba0 RCX: ffffffff8146cfd3
[ 135.233528] RDX: ffff88802264a540 RSI: ffffffff8146cfe0 RDI: 0000000000000001
[ 135.233929] RBP: ffff888022647e78 R08: 0000000000000001 R09: ffffed10044c8f66
[ 135.234325] R10: 0000000000000001 R11: 57525f4755424544 R12: ffff8880211162f0
[ 135.234722] R13: ffff8880211162f8 R14: ffff8880211162f0 R15: ffff88802264a540
[ 135.235122] FS: 00007f0327a07600(0000) GS:ffff88806c500000(0000) knlGS:0000000000000000
[ 135.235584] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 135.235912] CR2: 00007f032773e7f0 CR3: 0000000021bd4003 CR4: 0000000000770ef0
[ 135.236314] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 135.236713] DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400
[ 135.237114] PKRU: 55555554
[ 135.237276] Call Trace:
[ 135.237445] <TASK>
[ 135.237580] ? show_regs+0x6d/0x80
[ 135.237789] ? __warn+0xf3/0x390
[ 135.237987] ? find_bug+0x310/0x490
[ 135.238199] ? up_write+0x451/0x550
[ 135.238412] ? report_bug+0x2cb/0x4b0
[ 135.238636] ? up_write+0x451/0x550
[ 135.238853] ? up_write+0x452/0x550
[ 135.239065] ? handle_bug+0xf1/0x190
[ 135.239285] ? exc_invalid_op+0x3c/0x80
[ 135.239515] ? asm_exc_invalid_op+0x1f/0x30
[ 135.239768] ? __warn_printk+0x173/0x2e0
[ 135.240001] ? __warn_printk+0x180/0x2e0
[ 135.240235] ? up_write+0x451/0x550
[ 135.240445] ? madvise_unlock+0x17e/0x1a0
[ 135.240686] madvise_unlock+0xd4/0x1a0
[ 135.240913] do_madvise+0x14f/0x1a0
[ 135.241126] __x64_sys_madvise+0xb2/0x120
[ 135.241364] ? syscall_trace_enter+0x14f/0x280
[ 135.241647] x64_sys_call+0x19b1/0x2150
[ 135.241887] do_syscall_64+0x6d/0x140
[ 135.242113] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 135.242407] RIP: 0033:0x7f032763ee5d
[ 135.242619] 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 8b8
[ 135.243646] RSP: 002b:00007ffcaafd26c8 EFLAGS: 00000207 ORIG_RAX: 000000000000001c
[ 135.244075] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f032763ee5d
[ 135.244476] RDX: 0000000000000064 RSI: 0000000000004000 RDI: 0000000020e7f000
[ 135.244877] RBP: 00007ffcaafd26d0 R08: 00007ffcaafd2140 R09: 00007ffcaafd2700
[ 135.245279] R10: 0000000000000000 R11: 0000000000000207 R12: 00007ffcaafd2828
[ 135.245696] R13: 00000000004016da R14: 0000000000403e08 R15: 00007f0327a4e000
[ 135.246106] </TASK>
[ 135.246242] irq event stamp: 857
[ 135.246434] hardirqs last enabled at (857): [<ffffffff81663b55>] __up_console_sem+0x95/0xb0
[ 135.246915] hardirqs last disabled at (856): [<ffffffff81663b3a>] __up_console_sem+0x7a/0xb0
[ 135.247392] softirqs last enabled at (628): [<ffffffff8148c40e>] __irq_exit_rcu+0x10e/0x170
[ 135.247871] softirqs last disabled at (623): [<ffffffff8148c40e>] __irq_exit_rcu+0x10e/0x170
[ 135.248347] ---[ end trace 0000000000000000 ]---
"

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

> --
> 2.39.5