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From ab7647c2b04501297c50ce7cdb6f6895b9582d22 Mon Sep 17 00:00:00 2001
From: Greg Ungerer <gerg@kernel.org>
Date: Fri, 21 Apr 2023 00:21:38 +1000
Subject: [PATCH] fs: binfmt_elf_efpic: fix personality for non-fdpic ELF
The elf-fdpic loader hard sets the process personality to either
PER_LINUX_FDPIC for true elf-fdpic binaries or to PER_LINUX for
normal ELF binaries (in this case they would be constant displacement
compiled with -pie for example). The problem with that is that it
will lose any other bits that may be in the ELF header personality
("the "bug emulation" bits).
On the ARM architecture the ADDR_LIMIT_32BIT flag is used to signify
a normal 32bit binary - as opposed to a legacy 26bit address binary.
This matters since start_thread() will set the ARM CPSR register as
required based on this flag. If the elf-fdpic loader has lost this
bit the process will be mis-configured and crash out pretty quickly.
Modify elf-fdpic loaders personality setting for ELF binaries so that
it preserves the upper three bytes by using the SET_PERSONALITY macro
to set it. This macro in the generic case sets PER_LINUX but and
preserves the upper bytes. Architectures can override this for their
specific use case, and ARM does exactly this.
Signed-off-by: Greg Ungerer <gerg@kernel.org>
---
fs/binfmt_elf_fdpic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index a05eafcacfb2..f29ae1d96fd7 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -348,7 +348,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
if (elf_check_fdpic(&exec_params.hdr))
set_personality(PER_LINUX_FDPIC);
else
- set_personality(PER_LINUX);
+ SET_PERSONALITY(exec_params.hdr);
if (elf_read_implies_exec(&exec_params.hdr, executable_stack))
current->personality |= READ_IMPLIES_EXEC;
--
2.25.1
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