CVE-2025-39691

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

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

Theres 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: 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

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().

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/03b40bf5d0389ca23ae6857ee25789f0e0b47ce8
• https://git.kernel.org/stable/c/042cf48ecf67f72c8b3846c7fac678f472712ff3
• https://git.kernel.org/stable/c/3169edb8945c295cf89120fc6b2c35cfe3ad4c9e
• https://git.kernel.org/stable/c/70a09115da586bf662c3bae9c0c4a1b99251fad9
• https://git.kernel.org/stable/c/7375f22495e7cd1c5b3b5af9dcc4f6dffe34ce49
• https://git.kernel.org/stable/c/90b5193edb323fefbee0e4e5bc39ed89dcc37719
• https://git.kernel.org/stable/c/c58c6b532b7b69537cfd9ef701c7e37cdcf79dc4
• https://git.kernel.org/stable/c/c5aa6ba1127307ab5dc3773eaf40d73a3423841f
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html