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Date: Mon, 10 Jan 2022 17:49:47 +0530
From: Rohit Keshri <>
Subject: CVE-2021-4155 kernel: xfs: raw block device data leak
 in ioctl(XFS_IOC_ALLOCSP)


A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS
filesystem allowed for a size increase of files with unaligned size. A
local attacker could use this flaw to leak data on the XFS filesystem
otherwise not accessible to them.


(Kirill reported)
"the scenario is:

1)truncate() file by unaligned @size;
2)ioctl(XFS_IOC_ALLOCSP) to increase the file size up to 4096.

then xfs_ioc_space()->xfs_vn_setattr_size() never zeros [round_down(@size,
4096), @size]
and this raw block device data leaks away to user."

The patch for this issue:

Red Hat has assigned CVE-2021-4155 to this issue.

Kirill Tkhai (Virtuozzo Kernel team)

Rohit Keshri / Red Hat Product Security Team
PGP: OX01BC 858A 07B7 15C8 EF33 BFE2 2EEB 0CBC 84A4 4C2D for urgent response

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