[PATCH REPOST] fs: Preventing READ_IMPLIES_EXEC Propagation

[dongbo (E)]

From: Dong Bo <dongbo4@xxxxxxxxxx>

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.

This patch was originally posted and discussed here:
https://patchwork.kernel.org/patch/9685891/

Signed-off-by: Dong Bo <dongbo4@xxxxxxxxxx>
---
 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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