linux-kernel - Re: [PATCH V2] fs: fat: Prevent fsfuzzer from dominating the console

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Message-ID: <87a563w1ao.fsf@mail.parknet.co.jp>
Date: Fri, 20 Jun 2025 12:15:59 +0900
From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Li Chen <me@...ux.beauty>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] fs: fat: Prevent fsfuzzer from dominating the console

Li Chen <me@...ux.beauty> writes:

> From: Li Chen <chenl311@...natelecom.cn>
>
> fsfuzzer may make many invalid access for FAT-fs and generate many kmsg
> like "FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)".
>
> For platforms & os that enables hardware serial device whose speed are
> slow, this may cause softlockup easily.
>
> So let's ratelimit the error log.
>
> The log as below:
> [11916.242560] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.254485] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.266388] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.278287] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.290180] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.302068] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.313962] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.325848] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.337732] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.349619] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.361505] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.373391] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.385272] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.397144] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.409025] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.420909] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.432791] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.444674] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.456558] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.468446] FAT-fs (loop2): error, invalid access to FAT (entry 0x00000ccb)
> [11916.480352] watchdog: BUG: soft lockup - CPU#58 stuck for 26s! [cat:2446035]
> [11916.480357] Modules linked in: ...
> [11916.480503] CPU: 58 PID: 2446035 Comm: cat Kdump: loaded Tainted: ...
> [11916.480508] Hardware name: vclusters VSFT5000 B/VSFT5000 B, BIOS ...
> [11916.480510] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [11916.480513] pc : console_emit_next_record+0x1b4/0x288
> [11916.480524] lr : console_emit_next_record+0x1ac/0x288
> [11916.480525] sp : ffff80009bcdae90
> [11916.480527] x29: ffff80009bcdaec0 x28: ffff800082513810 x27: 0000000000000001
> [11916.480530] x26: 0000000000000001 x25: ffff800081f66000 x24: 0000000000000000
> [11916.480533] x23: 0000000000000000 x22: ffff80009bcdaf8f x21: 0000000000000001
> [11916.480535] x20: 0000000000000000 x19: ffff800082513810 x18: ffffffffffffffff
> [11916.480538] x17: 0000000000000002 x16: 0000000000000001 x15: ffff80009bcdab30
> [11916.480541] x14: 0000000000000000 x13: 205d353330363434 x12: 32545b5d36343438
> [11916.480543] x11: 652820544146206f x10: 7420737365636361 x9 : ffff800080159a6c
> [11916.480546] x8 : 69202c726f727265 x7 : 545b5d3634343836 x6 : 342e36313931315b
> [11916.480549] x5 : ffff800082513a01 x4 : ffff80009bcdad31 x3 : 0000000000000000
> [11916.480551] x2 : 00000000ffffffff x1 : 0000000001b9b000 x0 : ffff8000836cef00
> [11916.480554] Call trace:
> [11916.480557]  console_emit_next_record+0x1b4/0x288
> [11916.480560]  console_flush_all+0xcc/0x190
> [11916.480563]  console_unlock+0x78/0x138
> [11916.480565]  vprintk_emit+0x1c4/0x210
> [11916.480568]  vprintk_default+0x40/0x58
> [11916.480570]  vprintk+0x84/0xc8
> [11916.480572]  _printk+0x68/0xa0
> [11916.480578]  _fat_msg+0x6c/0xa0 [fat]
> [11916.480593]  __fat_fs_error+0xf8/0x118 [fat]
> [11916.480601]  fat_ent_read+0x164/0x238 [fat]
> [11916.480609]  fat_get_cluster+0x180/0x2c8 [fat]
> [11916.480617]  fat_get_mapped_cluster+0xb8/0x170 [fat]
>
> Signed-off-by: Li Chen <chenl311@...natelecom.cn>

Looks good.

Acked-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

Thanks.

> ---
> Changelog:
> v2: use fat_fs_error_ratelimit instead as suggested by OGAWA Hirofumi
>
>  fs/fat/fatent.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
> index 1db348f8f887a..a7061c2ad8e4d 100644
> --- a/fs/fat/fatent.c
> +++ b/fs/fat/fatent.c
> @@ -356,7 +356,7 @@ int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
>  
>  	if (!fat_valid_entry(sbi, entry)) {
>  		fatent_brelse(fatent);
> -		fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
> +		fat_fs_error_ratelimit(sb, "invalid access to FAT (entry 0x%08x)", entry);
>  		return -EIO;
>  	}

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>