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git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
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Chengfeng Ye
2d696c1ed3
For RFCOMM_RELEASE_ONHUP devices, rfcomm_tty_install() and
__rfcomm_release_dev() both use RFCOMM_TTY_OWNED to decide who drops the
initial tty_port reference. The release path tests the bit separately
from the install path setting it, so both can drop that reference.
The synchronous hangup does not prevent this race: port->tty is not
assigned until tty_port_open(), after installation. The following
interleaving is possible:
1. Install and release each obtain a reference with rfcomm_dev_get().
2. Release observes RFCOMM_TTY_OWNED clear.
3. Install sets RFCOMM_TTY_OWNED and drops the initial reference.
4. Release drops the same initial reference again.
5. TTY cleanup drops its reference and frees the device.
6. Release performs its final tty_port_put() on the freed port.
KASAN reported:
BUG: KASAN: slab-use-after-free in tty_port_put+0x22/0x190
Write of size 4 at addr ffff8881001d3d5c by task poc/92
Call Trace:
tty_port_put+0x22/0x190
rfcomm_dev_ioctl+0x1d4/0x1930
sock_do_ioctl+0x110/0x260
sock_ioctl+0x380/0x590
__x64_sys_ioctl+0x134/0x1c0
Allocated by task 88:
rfcomm_dev_ioctl+0x8f6/0x1930
sock_do_ioctl+0x110/0x260
sock_ioctl+0x380/0x590
__x64_sys_ioctl+0x134/0x1c0
Freed by task 65:
kfree+0x131/0x3c0
rfcomm_dev_destruct+0x23b/0x2f0
release_one_tty+0xc1/0x370
process_one_work+0x661/0x1090
Use test_and_set_bit() in both paths so that only the caller that changes
RFCOMM_TTY_OWNED from clear to set drops the initial reference. Each path
keeps its own lookup reference until release or TTY cleanup, preserving
the existing callback ordering and error handling.
Fixes: 80ea73378a ("Bluetooth: Fix unreleased rfcomm_dev reference")
Cc: [email protected]
Assisted-by: LLM
Signed-off-by: Chengfeng Ye <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>