[PATCH 5.4 094/434] x86/math-emu: Check __copy_from_user() result

Greg Kroah-Hartman
2019-12-29T17:45:17Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit e6b44ce1925a8329a937c57f0d60ba0d9bb5d226 ]

The new __must_check annotation on __copy_from_user() successfully
identified some code that has lacked the check since at least
linux-2.1.73:

arch/x86/math-emu/reg_ld_str.c:88:2: error: ignoring return value of \
function declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]
__copy_from_user(sti_ptr, s, 10);
^~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~
arch/x86/math-emu/reg_ld_str.c:1129:2: error: ignoring return value of \
function declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]
__copy_from_user(register_base + offset, s, other);
^~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/math-emu/reg_ld_str.c:1131:3: error: ignoring return value of \
function declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]
__copy_from_user(register_base, s + other, offset);
^~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In addition, the get_user()/put_user() helpers do not enforce a return
value check, but actually still require one. These have been missing for
even longer.

Change the internal wrappers around get_user()/put_user() to force
a signal and add a corresponding wrapper around __copy_from_user()
to check all such cases.

[ bp: Break long lines. ]

Fixes: 257e458057e5 ("Import 2.1.73")
Fixes: 9dd819a15162 ("uaccess: add missing __must_check attributes")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Bill Metzenthen <billm@melbpc.org.au>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191001142344.1274185-1-arnd@arndb.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/math-emu/fpu_system.h | 6 ++++--
arch/x86/math-emu/reg_ld_str.c | 6 +++---
2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index f98a0c956764..9b41391867dc 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -107,6 +107,8 @@ static inline bool seg_writable(struct desc_struct *d)
#define FPU_access_ok(y,z) if ( !access_ok(y,z) ) \
math_abort(FPU_info,SIGSEGV)
#define FPU_abort math_abort(FPU_info, SIGSEGV)
+#define FPU_copy_from_user(to, from, n) \
+ do { if (copy_from_user(to, from, n)) FPU_abort; } while (0)

#undef FPU_IGNORE_CODE_SEGV
#ifdef FPU_IGNORE_CODE_SEGV
@@ -122,7 +124,7 @@ static inline bool seg_writable(struct desc_struct *d)
#define FPU_code_access_ok(z) FPU_access_ok((void __user *)FPU_EIP,z)
#endif

-#define FPU_get_user(x,y) get_user((x),(y))
-#define FPU_put_user(x,y) put_user((x),(y))
+#define FPU_get_user(x,y) do { if (get_user((x),(y))) FPU_abort; } while (0)
+#define FPU_put_user(x,y) do { if (put_user((x),(y))) FPU_abort; } while (0)

#endif
diff --git a/arch/x86/math-emu/reg_ld_str.c b/arch/x86/math-emu/reg_ld_str.c
index f3779743d15e..fe6246ff9887 100644
--- a/arch/x86/math-emu/reg_ld_str.c
+++ b/arch/x86/math-emu/reg_ld_str.c
@@ -85,7 +85,7 @@ int FPU_load_extended(long double __user *s, int stnr)

RE_ENTRANT_CHECK_OFF;
FPU_access_ok(s, 10);
- __copy_from_user(sti_ptr, s, 10);
+ FPU_copy_from_user(sti_ptr, s, 10);
RE_ENTRANT_CHECK_ON;

return FPU_tagof(sti_ptr);
@@ -1126,9 +1126,9 @@ void frstor(fpu_addr_modes addr_modes, u_char __user *data_address)
/* Copy all registers in stack order. */
RE_ENTRANT_CHECK_OFF;
FPU_access_ok(s, 80);
- __copy_from_user(register_base + offset, s, other);
+ FPU_copy_from_user(register_base + offset, s, other);
if (offset)
- __copy_from_user(register_base, s + other, offset);
+ FPU_copy_from_user(register_base, s + other, offset);
RE_ENTRANT_CHECK_ON;

for (i = 0; i < 8; i++) {
--
2.20.1