From: "Eric W. Biederman" ebiederm@xmission.com

mainline inclusion from mainline-v5.8-rc1 commit e7f7785449a1f459a4a3ca92f82f56fb054dd2b9 category: bugfix bugzilla: 36868 CVE: NA

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In 2016 Linus moved install_exec_creds immediately after setup_new_exec, in binfmt_elf as a cleanup and as part of closing a potential information leak.

Perform the same cleanup for the other binary formats.

Different binary formats doing the same things the same way makes exec easier to reason about and easier to maintain.

Greg Ungerer reports:

I tested the the whole series on non-MMU m68k and non-MMU arm (exercising binfmt_flat) and it all tested out with no problems, so for the binfmt_flat changes:

Tested-by: Greg Ungerer gerg@linux-m68k.org

Ref: 9f834ec18def ("binfmt_elf: switch to new creds when switching to new mm") Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Greg Ungerer gerg@linux-m68k.org Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Ye Bin yebin10@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/x86/ia32/ia32_aout.c | 3 +-- fs/binfmt_aout.c | 2 +- fs/binfmt_elf_fdpic.c | 2 +- fs/binfmt_flat.c | 3 +-- 4 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c index 7dbbe9ffda173..8d78ea00d75fe 100644 --- a/arch/x86/ia32/ia32_aout.c +++ b/arch/x86/ia32/ia32_aout.c @@ -298,6 +298,7 @@ static int load_aout_binary(struct linux_binprm *bprm) set_personality_ia32(false);

setup_new_exec(bprm); + install_exec_creds(bprm);

regs->cs = __USER32_CS; regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 = @@ -314,8 +315,6 @@ static int load_aout_binary(struct linux_binprm *bprm) if (retval < 0) return retval;

- install_exec_creds(bprm); - if (N_MAGIC(ex) == OMAGIC) { unsigned long text_addr, map_size;

diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c index ca9725f18e005..af09b55d5ac52 100644 --- a/fs/binfmt_aout.c +++ b/fs/binfmt_aout.c @@ -244,6 +244,7 @@ static int load_aout_binary(struct linux_binprm * bprm) set_personality(PER_LINUX); #endif setup_new_exec(bprm); + install_exec_creds(bprm);

current->mm->end_code = ex.a_text + (current->mm->start_code = N_TXTADDR(ex)); @@ -256,7 +257,6 @@ static int load_aout_binary(struct linux_binprm * bprm) if (retval < 0) return retval;

- install_exec_creds(bprm);

if (N_MAGIC(ex) == OMAGIC) { unsigned long text_addr, map_size; diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index b53bb3729ac1e..60896c16f103c 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -357,6 +357,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) current->personality |= READ_IMPLIES_EXEC;

setup_new_exec(bprm); + install_exec_creds(bprm);

set_binfmt(&elf_fdpic_format);

@@ -438,7 +439,6 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) current->mm->start_stack = current->mm->start_brk + stack_size; #endif

- install_exec_creds(bprm); if (create_elf_fdpic_tables(bprm, current->mm, &exec_params, &interp_params) < 0) goto error; diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c index e4b59e76afb0d..bbeff9385d609 100644 --- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -517,6 +517,7 @@ static int load_flat_file(struct linux_binprm *bprm, /* OK, This is the point of no return */ set_personality(PER_LINUX_32BIT); setup_new_exec(bprm); + install_exec_creds(bprm); }

/* @@ -940,8 +941,6 @@ static int load_flat_binary(struct linux_binprm *bprm) } }

- install_exec_creds(bprm); - set_binfmt(&flat_format);

#ifdef CONFIG_MMU