diff mbox series

[5.4,186/314] powerpc/32s: Dont warn when mapping RO data ROX.

Message ID 20200623195347.776815416@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman June 23, 2020, 7:56 p.m. UTC 
From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ Upstream commit 4b19f96a81bceaf0bcf44d79c0855c61158065ec ]

Mapping RO data as ROX is not an issue since that data
cannot be modified to introduce an exploit.

PPC64 accepts to have RO data mapped ROX, as a trade off
between kernel size and strictness of protection.

On PPC32, kernel size is even more critical as amount of
memory is usually small.

Depending on the number of available IBATs, the last IBATs
might overflow the end of text. Only warn if it crosses
the end of RO data.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6499f8eeb2a36330e5c9fc1cee9a79374875bd54.1589866984.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/mm/book3s32/mmu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index 84d5fab94f8f8..1424a120710e4 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -187,6 +187,7 @@  void mmu_mark_initmem_nx(void)
 	int i;
 	unsigned long base = (unsigned long)_stext - PAGE_OFFSET;
 	unsigned long top = (unsigned long)_etext - PAGE_OFFSET;
+	unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
 	unsigned long size;
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S_601))
@@ -201,9 +202,10 @@  void mmu_mark_initmem_nx(void)
 		size = block_size(base, top);
 		size = max(size, 128UL << 10);
 		if ((top - base) > size) {
-			if (strict_kernel_rwx_enabled())
-				pr_warn("Kernel _etext not properly aligned\n");
 			size <<= 1;
+			if (strict_kernel_rwx_enabled() && base + size > border)
+				pr_warn("Some RW data is getting mapped X. "
+					"Adjust CONFIG_DATA_SHIFT to avoid that.\n");
 		}
 		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
 		base += size;