[PATCH v4 1/6] x86/elf: Add table to document READ_IMPLIES_EXEC
From: Kees Cook <hidden>
Date: 2020-02-25 05:13:37
Also in:
lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Add a table to document the current behavior of READ_IMPLIES_EXEC in preparation for changing the behavior. Signed-off-by: Kees Cook <redacted> Reviewed-by: Jason Gunthorpe <redacted> --- arch/x86/include/asm/elf.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 69c0f892e310..733f69c2b053 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h@@ -281,6 +281,25 @@ extern u32 elf_hwcap2; /* * 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, ia32 | has NX, x86_64 | + * ELF: | | | | + * -------------------------------|------------------|----------------| + * missing GNU_STACK | exec-all | exec-all | exec-all | + * GNU_STACK == RWX | exec-all | exec-all | exec-all | + * GNU_STACK == RW | exec-none | exec-none | 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. + * + * *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 + * */ #define elf_read_implies_exec(ex, executable_stack) \ (executable_stack != EXSTACK_DISABLE_X)
--
2.20.1
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