linux-kernel - Re: [PATCH 1/4] ext4: fix out of bounds punch offset

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Message-ID: <mfwnu23qasbm5nrvxon42xleoiswobikq5ogg7i6v4zawwhrid@dpjyzgwc2a2a>
Date: Wed, 30 Apr 2025 09:51:00 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, 
	wanghaichi0403@...il.com, yi.zhang@...wei.com, libaokun1@...wei.com, yukuai3@...wei.com, 
	yangerkun@...wei.com
Subject: Re: [PATCH 1/4] ext4: fix out of bounds punch offset

On Wed 30-04-25 09:12:58, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> Punching a hole with a start offset that exceeds max_end is not
> permitted and will result in a negative length in the
> truncate_inode_partial_folio() function while truncating the page cache,
> potentially leading to undesirable consequences.
> 
> A simple reproducer:
> 
>   truncate -s 9895604649994 /mnt/foo
>   xfs_io -c "pwrite 8796093022208 4096" /mnt/foo
>   xfs_io -c "fpunch 8796093022213 25769803777" /mnt/foo
> 
>   kernel BUG at include/linux/highmem.h:275!
>   Oops: invalid opcode: 0000 [#1] SMP PTI
>   CPU: 3 UID: 0 PID: 710 Comm: xfs_io Not tainted 6.15.0-rc3
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014
>   RIP: 0010:zero_user_segments.constprop.0+0xd7/0x110
>   RSP: 0018:ffffc90001cf3b38 EFLAGS: 00010287
>   RAX: 0000000000000005 RBX: ffffea0001485e40 RCX: 0000000000001000
>   RDX: 000000000040b000 RSI: 0000000000000005 RDI: 000000000040b000
>   RBP: 000000000040affb R08: ffff888000000000 R09: ffffea0000000000
>   R10: 0000000000000003 R11: 00000000fffc7fc5 R12: 0000000000000005
>   R13: 000000000040affb R14: ffffea0001485e40 R15: ffff888031cd3000
>   FS:  00007f4f63d0b780(0000) GS:ffff8880d337d000(0000)
>   knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 000000001ae0b038 CR3: 00000000536aa000 CR4: 00000000000006f0
>   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   Call Trace:
>    <TASK>
>    truncate_inode_partial_folio+0x3dd/0x620
>    truncate_inode_pages_range+0x226/0x720
>    ? bdev_getblk+0x52/0x3e0
>    ? ext4_get_group_desc+0x78/0x150
>    ? crc32c_arch+0xfd/0x180
>    ? __ext4_get_inode_loc+0x18c/0x840
>    ? ext4_inode_csum+0x117/0x160
>    ? jbd2_journal_dirty_metadata+0x61/0x390
>    ? __ext4_handle_dirty_metadata+0xa0/0x2b0
>    ? kmem_cache_free+0x90/0x5a0
>    ? jbd2_journal_stop+0x1d5/0x550
>    ? __ext4_journal_stop+0x49/0x100
>    truncate_pagecache_range+0x50/0x80
>    ext4_truncate_page_cache_block_range+0x57/0x3a0
>    ext4_punch_hole+0x1fe/0x670
>    ext4_fallocate+0x792/0x17d0
>    ? __count_memcg_events+0x175/0x2a0
>    vfs_fallocate+0x121/0x560
>    ksys_fallocate+0x51/0xc0
>    __x64_sys_fallocate+0x24/0x40
>    x64_sys_call+0x18d2/0x4170
>    do_syscall_64+0xa7/0x220
>    entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> Fix this by filtering out cases where the punching start offset exceeds
> max_end.
> 
> Fixes: 982bf37da09d ("ext4: refactor ext4_punch_hole()")
> Reported-by: Liebes Wang <wanghaichi0403@...il.com>
> Closes: https://lore.kernel.org/linux-ext4/ac3a58f6-e686-488b-a9ee-fc041024e43d@huawei.com/
> Tested-by: Liebes Wang <wanghaichi0403@...il.com>
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 94c7d2d828a6..4ec4a80b6879 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4016,7 +4016,7 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>  	WARN_ON_ONCE(!inode_is_locked(inode));
>  
>  	/* No need to punch hole beyond i_size */
> -	if (offset >= inode->i_size)
> +	if (offset >= inode->i_size || offset >= max_end)
>  		return 0;
>  
>  	/*
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR