linux-cve-announce - CVE-2025-39691: fs/buffer: fix use-after-free when call bh

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Message-ID: <2025090547-CVE-2025-39691-c878@gregkh>
Date: Fri,  5 Sep 2025 19:21:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39691: fs/buffer: fix use-after-free when call bh_read() helper

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

fs/buffer: fix use-after-free when call bh_read() helper

There's issue as follows:
BUG: KASAN: stack-out-of-bounds in end_buffer_read_sync+0xe3/0x110
Read of size 8 at addr ffffc9000168f7f8 by task swapper/3/0
CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.16.0-862.14.0.6.x86_64
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Call Trace:
 <IRQ>
 dump_stack_lvl+0x55/0x70
 print_address_description.constprop.0+0x2c/0x390
 print_report+0xb4/0x270
 kasan_report+0xb8/0xf0
 end_buffer_read_sync+0xe3/0x110
 end_bio_bh_io_sync+0x56/0x80
 blk_update_request+0x30a/0x720
 scsi_end_request+0x51/0x2b0
 scsi_io_completion+0xe3/0x480
 ? scsi_device_unbusy+0x11e/0x160
 blk_complete_reqs+0x7b/0x90
 handle_softirqs+0xef/0x370
 irq_exit_rcu+0xa5/0xd0
 sysvec_apic_timer_interrupt+0x6e/0x90
 </IRQ>

 Above issue happens when do ntfs3 filesystem mount, issue may happens
 as follows:
           mount                            IRQ
ntfs_fill_super
  read_cache_page
    do_read_cache_folio
      filemap_read_folio
        mpage_read_folio
	 do_mpage_readpage
	  ntfs_get_block_vbo
	   bh_read
	     submit_bh
	     wait_on_buffer(bh);
	                            blk_complete_reqs
				     scsi_io_completion
				      scsi_end_request
				       blk_update_request
				        end_bio_bh_io_sync
					 end_buffer_read_sync
					  __end_buffer_read_notouch
					   unlock_buffer

            wait_on_buffer(bh);--> return will return to caller

					  put_bh
					    --> trigger stack-out-of-bounds
In the mpage_read_folio() function, the stack variable 'map_bh' is
passed to ntfs_get_block_vbo(). Once unlock_buffer() unlocks and
wait_on_buffer() returns to continue processing, the stack variable
is likely to be reclaimed. Consequently, during the end_buffer_read_sync()
process, calling put_bh() may result in stack overrun.

If the bh is not allocated on the stack, it belongs to a folio.  Freeing
a buffer head which belongs to a folio is done by drop_buffers() which
will fail to free buffers which are still locked.  So it is safe to call
put_bh() before __end_buffer_read_notouch().

The Linux kernel CVE team has assigned CVE-2025-39691 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.4.297 with commit 70a09115da586bf662c3bae9c0c4a1b99251fad9
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.10.241 with commit 3169edb8945c295cf89120fc6b2c35cfe3ad4c9e
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.15.190 with commit 03b40bf5d0389ca23ae6857ee25789f0e0b47ce8
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.149 with commit c58c6b532b7b69537cfd9ef701c7e37cdcf79dc4
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.103 with commit c5aa6ba1127307ab5dc3773eaf40d73a3423841f
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.44 with commit 042cf48ecf67f72c8b3846c7fac678f472712ff3
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.16.4 with commit 90b5193edb323fefbee0e4e5bc39ed89dcc37719
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.17-rc3 with commit 7375f22495e7cd1c5b3b5af9dcc4f6dffe34ce49

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-39691
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/buffer.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/70a09115da586bf662c3bae9c0c4a1b99251fad9
	https://git.kernel.org/stable/c/3169edb8945c295cf89120fc6b2c35cfe3ad4c9e
	https://git.kernel.org/stable/c/03b40bf5d0389ca23ae6857ee25789f0e0b47ce8
	https://git.kernel.org/stable/c/c58c6b532b7b69537cfd9ef701c7e37cdcf79dc4
	https://git.kernel.org/stable/c/c5aa6ba1127307ab5dc3773eaf40d73a3423841f
	https://git.kernel.org/stable/c/042cf48ecf67f72c8b3846c7fac678f472712ff3
	https://git.kernel.org/stable/c/90b5193edb323fefbee0e4e5bc39ed89dcc37719
	https://git.kernel.org/stable/c/7375f22495e7cd1c5b3b5af9dcc4f6dffe34ce49