From dac853ae89043f1b7752875300faf614de43c74b Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Thu, 9 Jun 2011 20:05:18 +0200 Subject: [PATCH] exec: delay address limit change until point of no return Unconditionally changing the address limit to USER_DS and not restoring it to its old value in the error path is wrong because it prevents us using kernel memory on repeated calls to this function. This, in fact, breaks the fallback of hard coded paths to the init program from being ever successful if the first candidate fails to load. With this patch applied switching to USER_DS is delayed until the point of no return is reached which makes it possible to have a multi-arch rootfs with one arch specific init binary for each of the (hard coded) probed paths. Since the address limit is already set to USER_DS when start_thread() will be invoked, this redundancy can be safely removed. Signed-off-by: Mathias Krause Cc: Al Viro Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- arch/x86/kernel/process_32.c | 1 - arch/x86/kernel/process_64.c | 1 - fs/exec.c | 5 +---- 3 files changed, 1 insertion(+), 6 deletions(-) diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 8d12878..a3d0dc5 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -245,7 +245,6 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) { set_user_gs(regs, 0); regs->fs = 0; - set_fs(USER_DS); regs->ds = __USER_DS; regs->es = __USER_DS; regs->ss = __USER_DS; diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 6c9dd92..ca6f7ab 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -338,7 +338,6 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, regs->cs = _cs; regs->ss = _ss; regs->flags = X86_EFLAGS_IF; - set_fs(USER_DS); /* * Free the old FP and other extended state */ diff --git a/fs/exec.c b/fs/exec.c index ea5f748..97e0d52 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1093,6 +1093,7 @@ int flush_old_exec(struct linux_binprm * bprm) bprm->mm = NULL; /* We're using it now */ + set_fs(USER_DS); current->flags &= ~(PF_RANDOMIZE | PF_KTHREAD); flush_thread(); current->personality &= ~bprm->per_clear; @@ -1357,10 +1358,6 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) if (retval) return retval; - /* kernel module loader fixup */ - /* so we don't try to load run modprobe in kernel space. */ - set_fs(USER_DS); - retval = audit_bprm(bprm); if (retval) return retval; -- 2.7.4