The copy_user_handle_tail() clearly uses both from and to as pointers
to user-space memory. This triggers sparse warning on using the calls
to get and put to user-space. This can be fixed easily by changing the
call to take __user annotated pointer.s
arch/x86/lib/usercopy_64.c:68:21: warning: incorrect type in argument 1 (different address spaces)
arch/x86/lib/usercopy_64.c:68:21: expected void const volatile [noderef] <asn:1>*<noident>
arch/x86/lib/usercopy_64.c:68:21: got char *
arch/x86/lib/usercopy_64.c:70:21: warning: incorrect type in argument 1 (different address spaces)
arch/x86/lib/usercopy_64.c:70:21: expected void const volatile [noderef] <asn:1>*<noident>
arch/x86/lib/usercopy_64.c:70:21: got char *to
From Linus Torvalds:
On Thu, Mar 28, 2019 at 12:24 AM Borislav Petkov <[email protected]> wrote:
Well, but copy_user_generic() (which ends up calling the
copy_user_handle_tail() eventually) casts those __user pointers to
(__force void *). Converting them back to __user looks strange to me.
Linus?
Well, it does that because the x86 version of copy_user_generic() can
work in either direction, so it works when either the source or
destination (or both) are user pointers, but they don't _have_ to be.
So the "userness" of a pointer in that context is a bit ambiguous, and
so we've picked the pointers to be just plain "void *".
That said, arguably we should have gone the other way and just made
them both "__user" pointers, and do the cast the other way around.
But there's no absolutely right answer here, and nobody should ever
use copy_user_generic() directly (ie it is very much meant to be only
used as a internal helper for the cases that get the pointer
annotations right).
Signed-off-by: Ben Dooks <[email protected]>
---
arch/x86/include/asm/uaccess_64.h | 2 +-
arch/x86/lib/usercopy_64.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index a9d637bc301d..cbca2cb28939 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -208,7 +208,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
}
unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len);
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len);
unsigned long
mcsafe_handle_tail(char *to, char *from, unsigned len);
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index ee42bb0cbeb3..aa180424e77a 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -60,7 +60,7 @@ EXPORT_SYMBOL(clear_user);
* it is not necessary to optimize tail handling.
*/
__visible unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len)
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len)
{
for (; len; --len, to++) {
char c;
--
2.20.1
On 3/30/2019 5:26 PM, Ben Dooks wrote:
> The copy_user_handle_tail() clearly uses both from and to as pointers
> to user-space memory. This triggers sparse warning on using the calls
> to get and put to user-space. This can be fixed easily by changing the
> call to take __user annotated pointer.s
>
> arch/x86/lib/usercopy_64.c:68:21: warning: incorrect type in argument 1 (different address spaces)
> arch/x86/lib/usercopy_64.c:68:21: expected void const volatile [noderef] <asn:1>*<noident>
> arch/x86/lib/usercopy_64.c:68:21: got char *
> arch/x86/lib/usercopy_64.c:70:21: warning: incorrect type in argument 1 (different address spaces)
> arch/x86/lib/usercopy_64.c:70:21: expected void const volatile [noderef] <asn:1>*<noident>
> arch/x86/lib/usercopy_64.c:70:21: got char *to
>
> From Linus Torvalds:
>
> On Thu, Mar 28, 2019 at 12:24 AM Borislav Petkov <[email protected]> wrote:
>
> Well, but copy_user_generic() (which ends up calling the
> copy_user_handle_tail() eventually) casts those __user pointers to
> (__force void *). Converting them back to __user looks strange to me.
>
> Linus?
>
> Well, it does that because the x86 version of copy_user_generic() can
> work in either direction, so it works when either the source or
> destination (or both) are user pointers, but they don't _have_ to be.
>
> So the "userness" of a pointer in that context is a bit ambiguous, and
> so we've picked the pointers to be just plain "void *".
>
> That said, arguably we should have gone the other way and just made
> them both "__user" pointers, and do the cast the other way around.
>
> But there's no absolutely right answer here, and nobody should ever
> use copy_user_generic() directly (ie it is very much meant to be only
> used as a internal helper for the cases that get the pointer
> annotations right).
>
> Signed-off-by: Ben Dooks <[email protected]>
Reviewed-by: Mukesh Ojha <[email protected]>
Cheers,
-Mukesh
> ---
> arch/x86/include/asm/uaccess_64.h | 2 +-
> arch/x86/lib/usercopy_64.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
> index a9d637bc301d..cbca2cb28939 100644
> --- a/arch/x86/include/asm/uaccess_64.h
> +++ b/arch/x86/include/asm/uaccess_64.h
> @@ -208,7 +208,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
> }
>
> unsigned long
> -copy_user_handle_tail(char *to, char *from, unsigned len);
> +copy_user_handle_tail(char __user *to, char __user *from, unsigned len);
>
> unsigned long
> mcsafe_handle_tail(char *to, char *from, unsigned len);
> diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
> index ee42bb0cbeb3..aa180424e77a 100644
> --- a/arch/x86/lib/usercopy_64.c
> +++ b/arch/x86/lib/usercopy_64.c
> @@ -60,7 +60,7 @@ EXPORT_SYMBOL(clear_user);
> * it is not necessary to optimize tail handling.
> */
> __visible unsigned long
> -copy_user_handle_tail(char *to, char *from, unsigned len)
> +copy_user_handle_tail(char __user *to, char __user *from, unsigned len)
> {
> for (; len; --len, to++) {
> char c;
Commit-ID: b5dbb6799e3e5b8ebdce33b52b2d4ec9c66e15fe
Gitweb: https://git.kernel.org/tip/b5dbb6799e3e5b8ebdce33b52b2d4ec9c66e15fe
Author: Ben Dooks <[email protected]>
AuthorDate: Sat, 30 Mar 2019 11:56:24 +0000
Committer: Borislav Petkov <[email protected]>
CommitDate: Tue, 2 Apr 2019 10:38:51 +0200
x86/asm: Annotate copy_user_handle_tail() pointers with __user
copy_user_handle_tail() clearly uses both @from and @to as pointers to
user-space memory.
Currently, it triggers sparse warning on using the calls to get and put
to user-space which can be fixed easily by changing the call to take
__user annotated pointers:
arch/x86/lib/usercopy_64.c:68:21: warning: incorrect type in argument 1 (different address spaces)
arch/x86/lib/usercopy_64.c:68:21: expected void const volatile [noderef] <asn:1>*<noident>
arch/x86/lib/usercopy_64.c:68:21: got char *
arch/x86/lib/usercopy_64.c:70:21: warning: incorrect type in argument 1 (different address spaces)
arch/x86/lib/usercopy_64.c:70:21: expected void const volatile [noderef] <asn:1>*<noident>
arch/x86/lib/usercopy_64.c:70:21: got char *to
Linus further explains the reasoning why it was done this way:
On Thu, Mar 28, 2019 at 12:24 AM Borislav Petkov <[email protected]> wrote:
> Well, but copy_user_generic() (which ends up calling the
> copy_user_handle_tail() eventually) casts those __user pointers to
> (__force void *). Converting them back to __user looks strange to me.
>
> Linus?
Well, it does that because the x86 version of copy_user_generic() can
work in either direction, so it works when either the source or
destination (or both) are user pointers, but they don't _have_ to be.
So the "userness" of a pointer in that context is a bit ambiguous, and
so we've picked the pointers to be just plain "void *".
That said, arguably we should have gone the other way and just made
them both "__user" pointers, and do the cast the other way around.
But there's no absolutely right answer here, and nobody should ever
use copy_user_generic() directly (ie it is very much meant to be only
used as a internal helper for the cases that get the pointer
annotations right).
[ bp: massage. ]
Signed-off-by: Ben Dooks <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Mukesh Ojha <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/include/asm/uaccess_64.h | 2 +-
arch/x86/lib/usercopy_64.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index a9d637bc301d..cbca2cb28939 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -208,7 +208,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
}
unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len);
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len);
unsigned long
mcsafe_handle_tail(char *to, char *from, unsigned len);
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index ee42bb0cbeb3..aa180424e77a 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -60,7 +60,7 @@ EXPORT_SYMBOL(clear_user);
* it is not necessary to optimize tail handling.
*/
__visible unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len)
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len)
{
for (; len; --len, to++) {
char c;