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From: NeilBrown <>
To: Andrew Morton <>,
	Alexander Viro <>,
	Ingo Molnar <>,
	Dave Hansen <>,
	Andy Lutomirski <>,
	Peter Zijlstra <>
Cc: Xin Long <>,
Subject: [PATCH 2/3] x86: fix seq_file iteration for pat/memtype.c
Date: Fri, 05 Feb 2021 11:36:30 +1100
Message-ID: <161248539022.21478.13874455485854739066.stgit@noble1> (raw)
In-Reply-To: <161248518659.21478.2484341937387294998.stgit@noble1>

The memtype seq_file iterator allocates a buffer in the ->start and
->next functions and frees it in the ->show function.
The preferred handling for such resources is to free them in the
subsequent ->next or ->stop function call.

Since Commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration
code and interface") there is no guarantee that ->show will be called
after ->next, so this function can now leak memory.

So move the freeing of the buffer to ->next and ->stop.

Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
Cc: Xin Long <>
Signed-off-by: NeilBrown <>
 arch/x86/mm/pat/memtype.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 8f665c352bf0..ca311aaa67b8 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -1164,12 +1164,14 @@ static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
 static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+	kfree(v);
 	return memtype_get_idx(*pos);
 static void memtype_seq_stop(struct seq_file *seq, void *v)
+	kfree(v);
 static int memtype_seq_show(struct seq_file *seq, void *v)
@@ -1181,8 +1183,6 @@ static int memtype_seq_show(struct seq_file *seq, void *v)
-	kfree(entry_print);
 	return 0;

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05  0:36 [PATCH 0/3] Fix some seq_file users that were recently broken NeilBrown
2021-02-05  0:36 ` NeilBrown [this message]
2021-02-05  0:36 ` [PATCH 1/3] seq_file: document how per-entry resources are managed NeilBrown
2021-02-05  2:20   ` Matthew Wilcox
2021-02-05  0:36 ` [PATCH 3/3] net: fix iteration for sctp transport seq_files NeilBrown
2021-02-05 14:32   ` Marcelo Ricardo Leitner
2021-02-05 22:35 ` [PATCH 0/3] Fix some seq_file users that were recently broken Andrew Morton
2021-02-06 22:29   ` Jakub Kicinski
2021-02-07 21:11     ` Andrew Morton
2021-02-08 19:42       ` Jakub Kicinski
2021-02-07 22:45   ` NeilBrown

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