exec: delay address limit change until point of no return

commit dac853ae89043f1b7752875300faf614de43c74b upstream.

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 <minipli@googlemail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index f6c62667e30c89db95a8f2bc7054a6c12108f0dd..219141c5dadd6dd9d0d9cbe7f96e91979ef60134 100644 (file)
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -253,7 +253,6 @@ 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 17cb3295cbf773e94011e134c2a1fa2dfc2e62f1..0a18514b751fa7f03abd1be117d93efc739c082b 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -345,7 +345,6 @@ 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 11cfcced820aea2a31d11fb06d4400dfca5361f0..4afb996086d52b47810c6316bfc2b2069d765728 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1020,6 +1020,7 @@ int flush_old_exec(struct linux_binprm * bprm)
 
        bprm->mm = NULL;                /* We're using it now */
 
+       set_fs(USER_DS);
        current->flags &= ~PF_RANDOMIZE;
        flush_thread();
        current->personality &= ~bprm->per_clear;
@@ -1284,10 +1285,6 @@ 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;