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powerpc/signal: Use __get_user() to copy sigset_t 

Usually sigset_t is exactly 8B which is a "trivial" size and does not
warrant using __copy_from_user(). Use __get_user() directly in
anticipation of future work to remove the trivial size optimizations
from __copy_from_user().

The ppc32 implementation of get_sigset_t() previously called
copy_from_user() which, unlike __copy_from_user(), calls access_ok().
Replacing this w/ __get_user() (no access_ok()) is fine here since both
callsites in signal_32.c are preceded by an earlier access_ok().

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-11-cmr@codefail.de
This commit is contained in:
Christopher M. Riedl 2021-02-26 19:12:59 -06:00 committed by Michael Ellerman
parent 0f92433b8f
commit d3ccc97815
3 changed files with 10 additions and 3 deletions
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7
arch/powerpc/kernel/signal.h
View File

@ -19,6 +19,13 @@ extern int handle_signal32(struct ksignal *ksig, sigset_t *oldset,
extern int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
struct task_struct *tsk);
static inline int __get_user_sigset(sigset_t *dst, const sigset_t __user *src)
{
BUILD_BUG_ON(sizeof(sigset_t) != sizeof(u64));
return __get_user(dst->sig[0], (u64 __user *)&src->sig[0]);
}
#ifdef CONFIG_VSX
extern unsigned long copy_vsx_to_user(void __user *to,
struct task_struct *task);

2
arch/powerpc/kernel/signal_32.c
View File

@ -144,7 +144,7 @@ static inline int restore_general_regs(struct pt_regs *regs,
static inline int get_sigset_t(sigset_t *set, const sigset_t __user *uset)
{
return copy_from_user(set, uset, sizeof(*uset));
return __get_user_sigset(set, uset);
}
#define to_user_ptr(p) ((unsigned long)(p))

4
arch/powerpc/kernel/signal_64.c
View File

@ -708,7 +708,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
* We kill the task with a SIGSEGV in this situation.
*/
if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
if (__get_user_sigset(&set, &new_ctx->uc_sigmask))
do_exit(SIGSEGV);
set_current_blocked(&set);
@ -747,7 +747,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
if (!access_ok(uc, sizeof(*uc)))
goto badframe;
if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
if (__get_user_sigset(&set, &uc->uc_sigmask))
goto badframe;
set_current_blocked(&set);