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-rw-r--r--arch/arm/kernel/elf.c27
1 files changed, 23 insertions, 4 deletions
diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c
index 182422981386..254ab7138c85 100644
--- a/arch/arm/kernel/elf.c
+++ b/arch/arm/kernel/elf.c
@@ -78,13 +78,32 @@ void elf_set_personality(const struct elf32_hdr *x)
EXPORT_SYMBOL(elf_set_personality);
/*
- * Set READ_IMPLIES_EXEC if:
- * - the binary requires an executable stack
- * - we're running on a CPU which doesn't support NX.
+ * An executable for which elf_read_implies_exec() returns TRUE will
+ * have the READ_IMPLIES_EXEC personality flag set automatically.
+ *
+ * The decision process for determining the results are:
+ *
+ *              CPU: | lacks NX*  | has NX |
+ * ELF:              |            |           |
+ * ---------------------|------------|------------|
+ * missing PT_GNU_STACK | exec-all   | exec-all  |
+ * PT_GNU_STACK == RWX  | exec-all   | exec-stack |
+ * PT_GNU_STACK == RW   | exec-all  | exec-none |
+ *
+ * exec-all : all PROT_READ user mappings are executable, except when
+ * backed by files on a noexec-filesystem.
+ * exec-none : only PROT_EXEC user mappings are executable.
+ * exec-stack: only the stack and PROT_EXEC user mappings are executable.
+ *
+ * *this column has no architectural effect: NX markings are ignored by
+ * hardware, but may have behavioral effects when "wants X" collides with
+ * "cannot be X" constraints in memory permission flags, as in
+ * https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com
+ *
*/
int arm_elf_read_implies_exec(int executable_stack)
{
- if (executable_stack != EXSTACK_DISABLE_X)
+ if (executable_stack == EXSTACK_DEFAULT)
return 1;
if (cpu_architecture() < CPU_ARCH_ARMv6)
return 1;