linux-kernel - [RFC PATCH 3/3] x86/mm: cleanup prctl_enable_tagged_addr() nr

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Date: Thu,  7 Mar 2024 13:39:16 +0000
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...el.com>, Peter Zijlstra <peterz@...radead.org>, 
	Andy Lutomirski <luto@...nel.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, x86@...nel.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Yosry Ahmed <yosryahmed@...gle.com>
Subject: [RFC PATCH 3/3] x86/mm: cleanup prctl_enable_tagged_addr() nr_bits
 error checking

In prctl_enable_tagged_addr(), we check that nr_bits is in the correct
range, but we do so in a twisted if/else block where the correct case is
sandwiched between two error cases doing exactly the same thing.

Simplify the if condition and pull the correct case outside with the
rest of the success code path.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 arch/x86/kernel/process_64.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 33b268747bb7b..3f381906bbe1d 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -771,17 +771,13 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
 		return -EBUSY;
 	}
 
-	if (!nr_bits) {
-		mmap_write_unlock(mm);
-		return -EINVAL;
-	} else if (nr_bits <= LAM_U57_BITS) {
-		mm->context.lam_cr3_mask = X86_CR3_LAM_U57;
-		mm->context.untag_mask =  ~GENMASK(62, 57);
-	} else {
+	if (!nr_bits || nr_bits > LAM_U57_BITS) {
 		mmap_write_unlock(mm);
 		return -EINVAL;
 	}
 
+	mm->context.lam_cr3_mask = X86_CR3_LAM_U57;
+	mm->context.untag_mask =  ~GENMASK(62, 57);
 	write_cr3(__read_cr3() | mm->context.lam_cr3_mask);
 	set_tlbstate_lam_mode(mm);
 	set_bit(MM_CONTEXT_LOCK_LAM, &mm->context.flags);
-- 
2.44.0.278.ge034bb2e1d-goog