arm64: Validate tagged addresses in access_ok() called from kernel threads
commit5.4-rM2-2.2.x-imx-squasheddf325e05a6
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:63f0c60379
("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>
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5d8115f535
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1ac33be230
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@ -62,8 +62,13 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
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{
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unsigned long ret, limit = current_thread_info()->addr_limit;
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/*
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* Asynchronous I/O running in a kernel thread does not have the
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* TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
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* the user address before checking.
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*/
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if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
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test_thread_flag(TIF_TAGGED_ADDR))
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(current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
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addr = untagged_addr(addr);
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__chk_user_ptr(addr);
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