Patch "signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     signal-sh-use-force_sig-sigkill-instead-of-do_group_.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1254ea38526c087a183d6479a877108b3364d201
Author: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Date:   Wed Oct 20 12:43:52 2021 -0500

    signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)
    
    [ Upstream commit ce0ee4e6ac99606f3945f4d47775544edc3f7985 ]
    
    Today the sh code allocates memory the first time a process uses
    the fpu.  If that memory allocation fails, kill the affected task
    with force_sig(SIGKILL) rather than do_group_exit(SIGKILL).
    
    Calling do_group_exit from an exception handler can potentially lead
    to dead locks as do_group_exit is not designed to be called from
    interrupt context.  Instead use force_sig(SIGKILL) to kill the
    userspace process.  Sending signals in general and force_sig in
    particular has been tested from interrupt context so there should be
    no problems.
    
    Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
    Cc: Rich Felker <dalias@xxxxxxxx>
    Cc: linux-sh@xxxxxxxxxxxxxxx
    Fixes: 0ea820cf9bf5 ("sh: Move over to dynamically allocated FPU context.")
    Link: https://lkml.kernel.org/r/20211020174406.17889-6-ebiederm@xxxxxxxxxxxx
    Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/sh/kernel/cpu/fpu.c b/arch/sh/kernel/cpu/fpu.c
index ae354a2931e7e..fd6db0ab19288 100644
--- a/arch/sh/kernel/cpu/fpu.c
+++ b/arch/sh/kernel/cpu/fpu.c
@@ -62,18 +62,20 @@ void fpu_state_restore(struct pt_regs *regs)
 	}
 
 	if (!tsk_used_math(tsk)) {
-		local_irq_enable();
+		int ret;
 		/*
 		 * does a slab alloc which can sleep
 		 */
-		if (init_fpu(tsk)) {
+		local_irq_enable();
+		ret = init_fpu(tsk);
+		local_irq_disable();
+		if (ret) {
 			/*
 			 * ran out of memory!
 			 */
-			do_group_exit(SIGKILL);
+			force_sig(SIGKILL);
 			return;
 		}
-		local_irq_disable();
 	}
 
 	grab_fpu(regs);