powerpc/32s: Drop NULL addr verification (88f8c080) · Commits · 戴 / test

NULL addr is a user address. Don't waste time checking it. If someone tries to access it, it will SIGFAULT the same way as for address 1, so no need to make it special. The special case is when not doing a write, in that case we want to drop the entire function. This is now handled by 'dir' param and not by the nulity of 'to' anymore. Also make beginning of prevent_user_access() similar to beginning of allow_user_access(), and tell the compiler that writing in kernel space or with a 0 length is unlikely Signed-off-by:

Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/85e971223dfe6ace734637db1841678939a76155.1579866752.git.christophe.leroy@c-s.fr

arch/powerpc/include/asm/book3s/32/kup.h

+6 −4

Original line number	Diff line number	Diff line
		@@ -113,7 +113,7 @@ static __always_inline void allow_user_access(void __user *to, const void __user

		addr = (__force u32)to;

		if (!addr \|\| addr >= TASK_SIZE \|\| !size)
		if (unlikely(addr >= TASK_SIZE \|\| !size))
		return;

		end = min(addr + size, TASK_SIZE);
		@@ -124,16 +124,18 @@ static __always_inline void allow_user_access(void __user *to, const void __user
		static __always_inline void prevent_user_access(void __user to, const void __user from,
		u32 size, unsigned long dir)
		{
		u32 addr = (__force u32)to;
		u32 end = min(addr + size, TASK_SIZE);
		u32 addr, end;

		BUILD_BUG_ON(!__builtin_constant_p(dir));
		if (!(dir & KUAP_WRITE))
		return;

		if (!addr \|\| addr >= TASK_SIZE \|\| !size)
		addr = (__force u32)to;

		if (unlikely(addr >= TASK_SIZE \|\| !size))
		return;

		end = min(addr + size, TASK_SIZE);
		current->thread.kuap = 0;
		kuap_update_sr(mfsrin(addr) \| SR_KS, addr, end); /* set Ks */
		}

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