linux-kernel - [PATCH] mm/mprotect: Fix successful vma_merge() of next in do_mprotect

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Date:   Fri, 24 Feb 2023 16:20:55 -0500
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-next@...r.kernel.org
Cc:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Bert Karwatzki <spasswolf@....de>
Subject: [PATCH] mm/mprotect: Fix successful vma_merge() of next in do_mprotect_pkey()

If mprotect_fixup() successfully calls vma_merge() and replaces vma and
the next vma, then the tmp variable in the do_mprotect_pkey() is not
updated to point to the new vma end.  This results in the loop detecting
a gap between VMAs that does not exist.  Fix the faulty value of tmp by
setting it to the end location of the vma iterator at the end of the
loop.

Reported-by: Bert Karwatzki <spasswolf@....de>
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=217061
Fixes: 2286a6914c77 ("mm: change mprotect_fixup to vma iterator")
Link: https://lore.kernel.org/linux-mm/20230223120407.729110a6ecd1416ac59d9cb0@linux-foundation.org/
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mprotect.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 1d4843c97c2a..231929f119d9 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -832,6 +832,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		if (error)
 			break;
 
+		tmp = vma_iter_end(&vmi);
 		nstart = tmp;
 		prot = reqprot;
 	}
-- 
2.39.0