linux-kernel - [PATCH] fs: Preventing READ_IMPLIES

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Date:   Thu, 13 Apr 2017 20:33:52 +0800
From:   "dongbo (E)" <dongbo4@...wei.com>
To:     <viro@...iv.linux.org.uk>, <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Mark Rutland <mark.rutland@....com>,
        Linuxarm <linuxarm@...wei.com>,
        <linux-arm-kernel@...ts.infradead.org>, <catalin.marinas@....com>,
        <will.deacon@....com>
Subject: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation

From: Dong Bo <dongbo4@...wei.com>

In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set,
the flag is propagated to its child processes, even the elf
files are marked as not requiring executable stack. It may
cause superfluous operations on some arch, e.g.
__sync_icache_dcache on aarch64 due to a PROT_READ mmap is
also marked as PROT_EXEC.

Signed-off-by: Dong Bo <dongbo4@...wei.com>
---
 fs/binfmt_elf.c       | 2 ++
 fs/binfmt_elf_fdpic.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 5075fd5..c52e670 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	SET_PERSONALITY2(loc->elf_ex, &arch_state);
 	if (elf_read_implies_exec(loc->elf_ex, executable_stack))
 		current->personality |= READ_IMPLIES_EXEC;
+	else
+		current->personality &= ~READ_IMPLIES_EXEC;
  	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 		current->flags |= PF_RANDOMIZE;
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index cf93a4f..c4bc4d0 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
 		set_personality(PER_LINUX);
 	if (elf_read_implies_exec(&exec_params.hdr, executable_stack))
 		current->personality |= READ_IMPLIES_EXEC;
+	else
+		current->personality &= ~READ_IMPLIES_EXEC;
  	setup_new_exec(bprm);
 -- 1.9.1


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