Commit 98c738c8 authored by Nathan Lynch's avatar Nathan Lynch Committed by Michael Ellerman
Browse files

powerpc/rtas: mandate RTAS syscall filtering 



CONFIG_PPC_RTAS_FILTER has been optional but default-enabled since its
introduction. It's been enabled in enterprise distro kernels for a
while without causing ABI breakage that wasn't easily fixed, and it
prevents harmful abuses of the rtas syscall.

Let's make it unconditional.

Signed-off-by: default avatarNathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: default avatarAndrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221118150751.469393-10-nathanl@linux.ibm.com
parent f975b655

arch/powerpc/Kconfig

+0 −13
Original line number Diff line number Diff line
@@ -1044,19 +1044,6 @@ config PPC_SECVAR_SYSFS 
	  read/write operations on these variables. Say Y if you have

	  secure boot enabled and want to expose variables to userspace.



config PPC_RTAS_FILTER

	bool "Enable filtering of RTAS syscalls"

	default y

	depends on PPC_RTAS

	help

	  The RTAS syscall API has security issues that could be used to

	  compromise system integrity. This option enforces restrictions on the

	  RTAS calls and arguments passed by userspace programs to mitigate

	  these issues.



	  Say Y unless you know what you are doing and the filter is causing

	  problems for you.



endmenu



config ISA_DMA_API

arch/powerpc/kernel/rtas.c

+0 −16
Original line number Diff line number Diff line
@@ -1050,8 +1050,6 @@ noinstr struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log 
	return NULL;

}



#ifdef CONFIG_PPC_RTAS_FILTER



/*

 * The sys_rtas syscall, as originally designed, allows root to pass

 * arbitrary physical addresses to RTAS calls. A number of RTAS calls
@@ -1200,20 +1198,6 @@ static void __init rtas_syscall_filter_init(void) 
		rtas_filters[i].token = rtas_token(rtas_filters[i].name);

}



#else



static bool block_rtas_call(int token, int nargs,

			    struct rtas_args *args)

{

	return false;

}



static void __init rtas_syscall_filter_init(void)

{

}



#endif /* CONFIG_PPC_RTAS_FILTER */



/* We assume to be passed big endian arguments */

SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)

{