[PATCH] capabilities: fix undefined behavior in bit shift for CAP_TO_MASK

[Paul Moore]

On Mon, Oct 31, 2022 at 7:25 AM Gaosheng Cui <cuigaosheng1 at huawei.com> wrote:
>
> Shifting signed 32-bit value by 31 bits is undefined, so changing
> significant bit to unsigned. The UBSAN warning calltrace like below:
>
> UBSAN: shift-out-of-bounds in security/commoncap.c:1252:2
> left shift of 1 by 31 places cannot be represented in type 'int'
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x7d/0xa5
>  dump_stack+0x15/0x1b
>  ubsan_epilogue+0xe/0x4e
>  __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
>  cap_task_prctl+0x561/0x6f0
>  security_task_prctl+0x5a/0xb0
>  __x64_sys_prctl+0x61/0x8f0
>  do_syscall_64+0x58/0x80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>  </TASK>
>
> Fixes: e338d263a76a ("Add 64-bit capability support to the kernel")
> Signed-off-by: Gaosheng Cui <cuigaosheng1 at huawei.com>
> ---
>  include/uapi/linux/capability.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Merged into lsm/stable-6.1, and I'll plan to send this up to Linus
next week.  Thanks everyone!

-- 
paul-moore.com