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authorCatalin Marinas <catalin.marinas@arm.com>2019-12-05 13:57:36 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2019-12-06 12:02:56 +0000
commitdf325e05a682e9c624f471835c35bd3f870d5e8c (patch)
tree8086aa101be33fd4b519302a6d40050e673fb1b6 /arch/arm64
parentcba779d80a5d4ccb8bdeb799abd02bf7ba9be111 (diff)
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>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/uaccess.h7
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);