[syzbot] [tomoyo?] WARNING in tomoyo_write_control

[syzbot] [tomoyo?] WARNING in tomoyo_write_control

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    f932fb9b4074 Merge tag 'v6.13-rc2-ksmbd-server-fixes' of g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17855be8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=99a5586995ec03b2
dashboard link: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10a12d44580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11fc4730580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0d0c95f5364/disk-f932fb9b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/201cf3c7a7b5/vmlinux-f932fb9b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fcb972084579/bzImage-f932fb9b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5829 at mm/page_alloc.c:4727 __alloc_pages_noprof+0xeff/0x25b0 mm/page_alloc.c:4727
Modules linked in:
CPU: 1 UID: 0 PID: 5829 Comm: syz-executor788 Not tainted 6.13.0-rc2-syzkaller-00159-gf932fb9b4074 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
RIP: 0010:__alloc_pages_noprof+0xeff/0x25b0 mm/page_alloc.c:4727
Code: 24 2c 00 00 00 00 89 cd 0f 84 8b f9 ff ff 8b 34 24 48 89 da 8b 7c 24 08 e8 0e b3 fe ff e9 69 f9 ff ff c6 05 e1 44 16 0e 01 90 <0f> 0b 90 31 db e9 9f f3 ff ff 89 14 24 e8 9f a2 0c 00 8b 14 24 e9
RSP: 0018:ffffc90003e1f918 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 000000000000000b RDI: 0000000000040d40
RBP: 0000000000000000 R08: 0000000000000006 R09: 00000000003fffff
R10: 00000000003fffff R11: 0000000000000003 R12: 000000000000000b
R13: 0000000000040d40 R14: 1ffff920007c3f37 R15: 00000000003fffff
FS:  0000555571ba8380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000003ff000 CR3: 000000007b498000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 ___kmalloc_large_node+0x84/0x1b0 mm/slub.c:4228
 __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:4255
 __do_kmalloc_node mm/slub.c:4271 [inline]
 __kmalloc_noprof.cold+0xc/0x63 mm/slub.c:4295
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 tomoyo_write_control+0x267/0x13d0 security/tomoyo/common.c:2668
 vfs_write+0x24c/0x1150 fs/read_write.c:677
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f569c4ea2e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 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:00007ffddff422d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffddff424b8 RCX: 00007f569c4ea2e9
RDX: 00000000fffffdef RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f569c55d610 R08: 0000000000008000 R09: 0000000000008000
R10: 0000000000008000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffddff424a8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>


---
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[PATCH] tomoyo: Reject excessively long lines

[Leo Stone]

syzbot creates an anonymous memory region, and then issues a
write syscall from the new memory region to a sysfs entry controlled by
tomoyo, specifying a buffer size of just under 2 GB (the actual size of
the buffer is ~32 MB). Because tomoyo_write_control will double the
size of head->write_buf every time it runs out of space for the current
line, and everything in the zero-initialized buffer is on the same line,
the function will eventually issue a kzalloc with a size that is too large,
triggering the warning.

Reject writes with excessively long lines.

Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
Signed-off-by: Leo Stone <leocstone@gmail.com>
---
 security/tomoyo/common.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index 5c7b059a332a..0c75be949c9d 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -2665,6 +2665,10 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head,
 
 		if (head->w.avail >= head->writebuf_size - 1) {
 			const int len = head->writebuf_size * 2;
+			if (len > KMALLOC_MAX_SIZE) {
+				error = -EINVAL;
+				break;
+			}
 			char *cp = kzalloc(len, GFP_NOFS);
 
 			if (!cp) {
-- 
2.43.0

[PATCH] tomoyo: prevent bad buffer size in tracing_cpumask_write

[Lizhi Xu]

User input a too large buffer size 0xfffffdeful, although it is truncated to
MAX_RW_COUNT in vfs_write, its value is still too large, causing warning when
allocating memory in tomoyo_write_control.

Add a check for it to avoid this case.

Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
Tested-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 security/tomoyo/common.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index 5c7b059a332a..f63388c2fffd 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -2654,6 +2654,8 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head,
 
 	if (!head->write)
 		return -EINVAL;
+	if (avail_len > KMALLOC_MAX_SIZE)
+		return -EINVAL;
 	if (mutex_lock_interruptible(&head->io_sem))
 		return -EINTR;
 	cp0 = head->write_buf;
-- 
2.43.0

Re: [PATCH] tomoyo: prevent bad buffer size in tracing_cpumask_write

[Tetsuo Handa]

On 2024/12/16 17:19, Lizhi Xu wrote:
> User input a too large buffer size 0xfffffdeful, although it is truncated to
> MAX_RW_COUNT in vfs_write, its value is still too large, causing warning when
> allocating memory in tomoyo_write_control.
> 
> Add a check for it to avoid this case.

Thank you for a patch. But I don't think this fix is correct, for one can make
head->writebuf_size too large by writing chunks without new line for many times.

> 
> Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
> Tested-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> ---
>  security/tomoyo/common.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
> index 5c7b059a332a..f63388c2fffd 100644
> --- a/security/tomoyo/common.c
> +++ b/security/tomoyo/common.c
> @@ -2654,6 +2654,8 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head,
>  
>  	if (!head->write)
>  		return -EINVAL;
> +	if (avail_len > KMALLOC_MAX_SIZE)
> +		return -EINVAL;
>  	if (mutex_lock_interruptible(&head->io_sem))
>  		return -EINTR;
>  	cp0 = head->write_buf;

[PATCH] tomoyo: don't emit warning in tomoyo_write_control()

[Tetsuo Handa]

syzbot is reporting too large allocation warning at tomoyo_write_control(),
for one can write a very very long line without new line character. To fix
this warning, I use __GFP_NOWARN rather than checking for KMALLOC_MAX_SIZE,
for practically a valid line should be always shorter than 32KB where the
"too small to fail" memory-allocation rule applies.

One might try to write a valid line that is longer than 32KB, but such
request will likely fail with -ENOMEM. Therefore, I feel that separately
returning -EINVAL when a line is longer than KMALLOC_MAX_SIZE is redundant.
There is no need to distinguish over-32KB and over-KMALLOC_MAX_SIZE.

Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
Reported-by: Leo Stone <leocstone@gmail.com>
Closes: https://lkml.kernel.org/r/20241216021459.178759-2-leocstone@gmail.com
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 security/tomoyo/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index 5c7b059a332a..972664962e8f 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -2665,7 +2665,7 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head,
 
 		if (head->w.avail >= head->writebuf_size - 1) {
 			const int len = head->writebuf_size * 2;
-			char *cp = kzalloc(len, GFP_NOFS);
+			char *cp = kzalloc(len, GFP_NOFS | __GFP_NOWARN);
 
 			if (!cp) {
 				error = -ENOMEM;
-- 
2.43.5