The following commit has been merged into the core/core branch of tip: Commit-ID: 9d9e435f3f2492bfd196acacb61cc9a9212d8170 Gitweb: https://git.kernel.org/tip/9d9e435f3f2492bfd196acacb61cc9a9212d8170 Author: Kees Cook <keescook@xxxxxxxxxxxx> AuthorDate: Thu, 26 Mar 2020 23:48:15 -07:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 20 Apr 2020 15:28:40 +02:00 x86/elf: Add table to document READ_IMPLIES_EXEC Add a table to document the current behavior of READ_IMPLIES_EXEC in preparation for changing the behavior. Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200327064820.12602-2-keescook@xxxxxxxxxxxx --- 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 69c0f89..ee459d4 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 PT_GNU_STACK | exec-all | exec-all | exec-all | + * PT_GNU_STACK == RWX | exec-all | exec-all | exec-all | + * PT_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@xxxxxxxxxxxx + * */ #define elf_read_implies_exec(ex, executable_stack) \ (executable_stack != EXSTACK_DISABLE_X)
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