linux-kernel - [PATCH 08/20] signal/sparc: In setup_tsb_params convert open coded BUG into BUG

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Date:   Wed, 20 Oct 2021 12:43:54 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        David Miller <davem@...emloft.net>, sparclinux@...r.kernel.org
Subject: [PATCH 08/20] signal/sparc: In setup_tsb_params convert open coded BUG into BUG

The function setup_tsb_params has exactly one caller tsb_grow.  The
function tsb_grow passes in a tsb_bytes value that is between 8192 and
1048576 inclusive, and is guaranteed to be a power of 2.  The function
setup_tsb_params verifies this property with a switch statement and
then prints an error and causes the task to exit if this is not true.

In practice that print statement can never be reached because tsb_grow
never passes in a bad tsb_size.  So if tsb_size ever gets a bad value
that is a kernel bug.

So replace the do_exit which is effectively an open coded version of
BUG() with an actuall call to BUG().  Making it clearer that this
is a case that can never, and should never happen.

Cc: David Miller <davem@...emloft.net>
Cc: sparclinux@...r.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 arch/sparc/mm/tsb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/mm/tsb.c b/arch/sparc/mm/tsb.c
index 0dce4b7ff73e..912205787161 100644
--- a/arch/sparc/mm/tsb.c
+++ b/arch/sparc/mm/tsb.c
@@ -266,7 +266,7 @@ static void setup_tsb_params(struct mm_struct *mm, unsigned long tsb_idx, unsign
 	default:
 		printk(KERN_ERR "TSB[%s:%d]: Impossible TSB size %lu, killing process.\n",
 		       current->comm, current->pid, tsb_bytes);
-		do_exit(SIGSEGV);
+		BUG();
 	}
 	tte |= pte_sz_bits(page_sz);

-- 
2.20.1