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

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Message-ID: <20250430011301.1106457-1-yi.zhang@huaweicloud.com>
Date: Wed, 30 Apr 2025 09:12:58 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: 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,
	yi.zhang@...weicloud.com,
	libaokun1@...wei.com,
	yukuai3@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH 1/4] ext4: fix out of bounds punch offset

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>
---
 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