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Message-ID: <3329905c-7eb8-400a-8f0a-d87cff979b5b@p183>
Date: Fri, 21 Jun 2024 21:54:50 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org
Subject: [PATCH] ELF: fix kernel.randomize_va_space double read
ELF loader uses "randomize_va_space" twice. It is sysctl and can change
at any moment, so 2 loads could see 2 different values in theory with
unpredictable consequences.
Issue exactly one load for consistent value across one exec.
Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
fs/binfmt_elf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1003,7 +1003,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
if (elf_read_implies_exec(*elf_ex, executable_stack))
current->personality |= READ_IMPLIES_EXEC;
- if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+ const int snapshot_randomize_va_space = READ_ONCE(randomize_va_space);
+ if (!(current->personality & ADDR_NO_RANDOMIZE) && snapshot_randomize_va_space)
current->flags |= PF_RANDOMIZE;
setup_new_exec(bprm);
@@ -1251,7 +1252,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
mm->end_data = end_data;
mm->start_stack = bprm->p;
- if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) {
+ if ((current->flags & PF_RANDOMIZE) && (snapshot_randomize_va_space > 1)) {
/*
* For architectures with ELF randomization, when executing
* a loader directly (i.e. no interpreter listed in ELF
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