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Commit 1c9bb1a0 authored by Paul Mackerras's avatar Paul Mackerras
Browse files

[POWERPC] Fix register save area alignment for swapcontext syscall 



For 32-bit processes, the getcontext side of the swapcontext system
call (i.e. the saving of the context when the first argument is
non-NULL) has to set the ctx->uc_mcontext.uc_regs pointer to the place
where it saves the registers.  Which it does, but it doesn't ensure
that the pointer is 16-byte aligned.  16-byte alignment is needed
because the Altivec/VMX registers are saved in there, and they need to
be on a 16-byte boundary.

This fixes it by ensuring the appropriate alignment of the pointer.
This issue was pointed out by Jakub Jelinek.

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent bb63ab13

arch/powerpc/kernel/signal_32.c

+13 −3
Original line number Diff line number Diff line
@@ -835,11 +835,21 @@ long sys_swapcontext(struct ucontext __user *old_ctx, 
		return -EINVAL;



	if (old_ctx != NULL) {

		struct mcontext __user *mctx;



		/*

		 * old_ctx might not be 16-byte aligned, in which

		 * case old_ctx->uc_mcontext won't be either.

		 * Because we have the old_ctx->uc_pad2 field

		 * before old_ctx->uc_mcontext, we need to round down

		 * from &old_ctx->uc_mcontext to a 16-byte boundary.

		 */

		mctx = (struct mcontext __user *)

			((unsigned long) &old_ctx->uc_mcontext & ~0xfUL);

		if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))

		    || save_user_regs(regs, &old_ctx->uc_mcontext, 0)

		    || save_user_regs(regs, mctx, 0)

		    || put_sigset_t(&old_ctx->uc_sigmask, &current->blocked)

		    || __put_user(to_user_ptr(&old_ctx->uc_mcontext),

			    &old_ctx->uc_regs))

		    || __put_user(to_user_ptr(mctx), &old_ctx->uc_regs))

			return -EFAULT;

	}

	if (new_ctx == NULL)