[syzbot] WARNING in __get_free_pages

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: debe436e77c7 Merge tag 'ext4_for_linus' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10bca72ab00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9d7259f0deb293aa
dashboard link: https://syzkaller.appspot.com/bug?extid=23a02c7df2cf2bc93fa2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+23a02c...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 current_gfp_context include/linux/sched/mm.h:195 [inline]
WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 __alloc_pages+0x45d/0x500 mm/page_alloc.c:5356
Modules linked in:
CPU: 3 PID: 16525 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:__alloc_pages+0x45d/0x500 mm/page_alloc.c:5344
Code: be c9 00 00 00 48 c7 c7 20 4a 97 89 c6 05 62 32 a7 0b 01 e8 74 9a 42 07 e9 6a ff ff ff 0f 0b e9 a0 fd ff ff 40 80 e5 3f eb 88 <0f> 0b e9 18 ff ff ff 4c 89 ef 44 89 e6 45 31 ed e8 1e 76 ff ff e9
RSP: 0018:ffffc90023b87850 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff92004770f0b RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000033 RDI: 0000000000010cc1
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff81bb4686 R11: 0000000000000001 R12: ffffffff902c1960
R13: 0000000000000033 R14: 0000000000000000 R15: ffff88804cf64a30
FS: 0000000000000000(0000) GS:ffff88802cd00000(0063) knlGS:00000000f44b4b40
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000002c921000 CR3: 000000004f507000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
__get_free_pages+0x8/0x40 mm/page_alloc.c:5418
raw_cmd_copyin drivers/block/floppy.c:3113 [inline]
raw_cmd_ioctl drivers/block/floppy.c:3160 [inline]
fd_locked_ioctl+0x12e5/0x2820 drivers/block/floppy.c:3528
fd_ioctl drivers/block/floppy.c:3555 [inline]
fd_compat_ioctl+0x891/0x1b60 drivers/block/floppy.c:3869
compat_blkdev_ioctl+0x3b8/0x810 block/ioctl.c:662
__do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:972
do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
__do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf6eba549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f44b45fc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000258
RDX: 0000000020000400 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
----------------
Code disassembly (best guess):
0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
a: 10 06 adc %al,(%rsi)
c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
10: 10 07 adc %al,(%rdi)
12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
16: 10 08 adc %cl,(%rax)
18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1c: 00 00 add %al,(%rax)
1e: 00 00 add %al,(%rax)
20: 00 51 52 add %dl,0x52(%rcx)
23: 55 push %rbp
24: 89 e5 mov %esp,%ebp
26: 0f 34 sysenter
28: cd 80 int $0x80
* 2a: 5d pop %rbp <-- trapping instruction
2b: 5a pop %rdx
2c: 59 pop %rcx
2d: c3 retq
2e: 90 nop
2f: 90 nop
30: 90 nop
31: 90 nop
32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi


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[Xiongwei Song]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
8ab77458790

commit 0921cbb7e62f2aac73da86fff458814d9b0a846b (HEAD)
Author: Xiongwei Song <sxw...@gmail.com>
Date: Mon Nov 15 16:06:19 2021 +0800

floppy: Add max size check for user space request

We need to check the max request size that is from user space before
allocating pages. If the request size exceeds the limit, return -EINVAL.

Signed-off-by: Xiongwei Song <sxw...@gmail.com>

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index c4267da716fe..52112ed59dd0 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3081,6 +3081,8 @@ static void raw_cmd_free(struct floppy_raw_cmd **ptr)
}
}

+#define MAX_LEN (1UL << MAX_ORDER << PAGE_SHIFT)
+
static int raw_cmd_copyin(int cmd, void __user *param,
struct floppy_raw_cmd **rcmd)
{
@@ -3108,7 +3110,7 @@ static int raw_cmd_copyin(int cmd, void __user *param,
ptr->resultcode = 0;

if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
- if (ptr->length <= 0)
+ if (ptr->length <= 0 || ptr->length >= MAX_LEN)
return -EINVAL;
ptr->kernel_data = (char *)fd_dma_mem_alloc(ptr->length);
fallback_on_nodma_alloc(&ptr->kernel_data, ptr->length);


Regards,
Xiongwei

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[syzbot]

> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

This crash does not have a reproducer. I cannot test it.