From: Catalin Marinas catalin.marinas@arm.com
commit df325e05a682e9c624f471835c35bd3f870d5e8c upstream.
__range_ok(), invoked from access_ok(), clears the tag of the user address only if CONFIG_ARM64_TAGGED_ADDR_ABI is enabled and the thread opted in to the relaxed ABI. The latter sets the TIF_TAGGED_ADDR thread flag. In the case of asynchronous I/O (e.g. io_submit()), the access_ok() may be called from a kernel thread. Since kernel threads don't have TIF_TAGGED_ADDR set, access_ok() will fail for valid tagged user addresses. Example from the ffs_user_copy_worker() thread:
use_mm(io_data->mm); ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data); unuse_mm(io_data->mm);
Relax the __range_ok() check to always untag the user address if called in the context of a kernel thread. The user pointers would have already been checked via aio_setup_rw() -> import_{single_range,iovec}() at the time of the asynchronous I/O request.
Fixes: 63f0c6037965 ("arm64: Introduce prctl() options to control the tagged user addresses ABI") Cc: stable@vger.kernel.org # 5.4.x- Cc: Will Deacon will@kernel.org Reported-by: Evgenii Stepanov eugenis@google.com Tested-by: Evgenii Stepanov eugenis@google.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/include/asm/uaccess.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -62,8 +62,13 @@ static inline unsigned long __range_ok(c { unsigned long ret, limit = current_thread_info()->addr_limit;
+ /* + * Asynchronous I/O running in a kernel thread does not have the + * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag + * the user address before checking. + */ if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) && - test_thread_flag(TIF_TAGGED_ADDR)) + (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR))) addr = untagged_addr(addr);
__chk_user_ptr(addr);