unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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ELF: fix kernel.randomize_va_space double read

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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@gmail.com>
Link: https://lore.kernel.org/r/3329905c-7eb8-400a-8f0a-d87cff979b5b@p183
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Alexey Dobriyan 2024-06-21 21:54:50 +03:00 committed by Kees Cook
parent 60371f43e5
commit 2a97388a80
1 changed files with 3 additions and 2 deletions
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5
fs/binfmt_elf.c
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@ -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);
@ -1285,7 +1286,7 @@ 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