diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2019-12-05 13:57:36 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2019-12-06 12:02:56 +0000 |
| commit | df325e05a682e9c624f471835c35bd3f870d5e8c (patch) | |
| tree | 8086aa101be33fd4b519302a6d40050e673fb1b6 | |
| parent | cba779d80a5d4ccb8bdeb799abd02bf7ba9be111 (diff) | |
| download | linux-df325e05a682e9c624f471835c35bd3f870d5e8c.tar.bz2 | |
arm64: Validate tagged addresses in access_ok() called from kernel threads
__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>
| -rw-r--r-- | arch/arm64/include/asm/uaccess.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 097d6bfac0b7..cccb03e1ab1f 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -62,8 +62,13 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si { 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); |