From 4549c3ea3160fa8b3f37dfe2f957657bb265eda9 Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date: Wed, 6 Oct 2021 01:55:20 +0530
Subject: [PATCH] powerpc/lib: Add helper to check if offset is within
conditional branch range
References: bsc#1188983 CVE-2021-34556 bsc#1188985 CVE-2021-35477
Patch-mainline: v5.15-rc5
Git-commit: 4549c3ea3160fa8b3f37dfe2f957657bb265eda9
Add a helper to check if a given offset is within the branch range for a
powerpc conditional branch instruction, and update some sites to use the
new helper.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/442b69a34ced32ca346a0d9a855f3f6cfdbbbd41.1633464148.git.naveen.n.rao@linux.vnet.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/include/asm/code-patching.h | 1 +
arch/powerpc/lib/code-patching.c | 7 ++++++-
arch/powerpc/net/bpf_jit.h | 7 +------
3 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -23,6 +23,7 @@
#define BRANCH_ABSOLUTE 0x2
bool is_offset_in_branch_range(long offset);
+bool is_offset_in_cond_branch_range(long offset);
unsigned int create_branch(const unsigned int *addr,
unsigned long target, int flags);
unsigned int create_cond_branch(const unsigned int *addr,
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -228,6 +228,11 @@ bool is_offset_in_branch_range(long offset)
return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
}
+bool is_offset_in_cond_branch_range(long offset)
+{
+ return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
+}
+
/*
* Helper to check if a given instruction is a conditional branch
* Derived from the conditional checks in analyse_instr()
@@ -280,7 +285,7 @@ int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
offset = offset - (unsigned long)addr;
/* Check we can represent the target in the instruction format */
- if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
+ if (!is_offset_in_cond_branch_range(offset))
return 0;
/* Mask out the flags and target, so they don't step on each other. */
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -78,11 +78,6 @@
#define PPC_FUNC_ADDR(d,i) do { PPC_LI32(d, i); } while(0)
#endif
-static inline bool is_nearbranch(int offset)
-{
- return (offset < 32768) && (offset >= -32768);
-}
-
/*
* The fly in the ointment of code size changing from pass to pass is
* avoided by padding the short branch case with a NOP. If code size differs
@@ -91,7 +86,7 @@ static inline bool is_nearbranch(int offset)
* state.
*/
#define PPC_BCC(cond, dest) do { \
- if (is_nearbranch((dest) - (ctx->idx * 4))) { \
+ if (is_offset_in_cond_branch_range((long)(dest) - (ctx->idx * 4))) { \
PPC_BCC_SHORT(cond, dest); \
PPC_NOP(); \
} else { \
--
2.31.1