Commit-ID: b5dbb6799e3e5b8ebdce33b52b2d4ec9c66e15fe Gitweb: https://git.kernel.org/tip/b5dbb6799e3e5b8ebdce33b52b2d4ec9c66e15fe Author: Ben Dooks <ben.do...@codethink.co.uk> AuthorDate: Sat, 30 Mar 2019 11:56:24 +0000 Committer: Borislav Petkov <b...@suse.de> 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 <b...@alien8.de> 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 <ben.do...@codethink.co.uk> Signed-off-by: Borislav Petkov <b...@suse.de> Reviewed-by: Mukesh Ojha <mo...@codeaurora.org> Cc: Alexey Dobriyan <adobri...@gmail.com> Cc: Dan Williams <dan.j.willi...@intel.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Ingo Molnar <mi...@redhat.com> Cc: Jann Horn <ja...@google.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mikulas Patocka <mpato...@redhat.com> Cc: mi...@redhat.co Cc: Thomas Gleixner <t...@linutronix.de> Cc: x86-ml <x...@kernel.org> Link: https://lkml.kernel.org/r/20190330115624.4000-1-ben.do...@codethink.co.uk --- 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;
