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Date:   Mon,  3 Oct 2022 18:45:31 -0400
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Message-ID: <20221003224531.1930646-1-sethjenkins@google.com>
Subject: [PATCH] mm: /proc/pid/smaps_rollup: fix no vma's null-deref
From:   FirstName LastName <sethjenkins@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Seth Jenkins <sethjenkins@google.com>,
        Jann Horn <jannh@google.com>, linux-mm@kvack.org,
        stable@vger.kernel.org
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From: Seth Jenkins <sethjenkins@google.com>

Commit 258f669e7e88 ("mm: /proc/pid/smaps_rollup: convert to single value
seq_file") introduced a null-deref if there are no vma's in the task in
show_smaps_rollup.

Fixes: 258f669e7e88 ("mm: /proc/pid/smaps_rollup: convert to single value seq_file")
Cc: stable@vger.kernel.org
Signed-off-by: Seth Jenkins <sethjenkins@google.com>
---
 fs/proc/task_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4e0023643f8b..1e7bbc0873a4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -969,7 +969,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
 		vma = vma->vm_next;
 	}
 
-	show_vma_header_prefix(m, priv->mm->mmap->vm_start,
+	show_vma_header_prefix(m, priv->mm->mmap ? priv->mm->mmap->vm_start : 0,
 			       last_vma_end, 0, 0, 0, 0);
 	seq_pad(m, ' ');
 	seq_puts(m, "[rollup]\n");
-- 
2.38.0.rc1.362.ged0d419d3c-goog