+ x86-fix-seq_file-iteration-for-pat-memtypec.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: x86: fix seq_file iteration for pat/memtype.c
has been added to the -mm tree.  Its filename is
     x86-fix-seq_file-iteration-for-pat-memtypec.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/x86-fix-seq_file-iteration-for-pat-memtypec.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/x86-fix-seq_file-iteration-for-pat-memtypec.patch

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------------------------------------------------------
From: NeilBrown <neilb@suse.de>
Subject: x86: fix seq_file iteration for pat/memtype.c

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.

Link: https://lkml.kernel.org/r/161248539022.21478.13874455485854739066.stgit@noble1
Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/mm/pat/memtype.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/pat/memtype.c~x86-fix-seq_file-iteration-for-pat-memtypec
+++ a/arch/x86/mm/pat/memtype.c
@@ -1164,12 +1164,14 @@ static void *memtype_seq_start(struct se
 
 static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
+	kfree(v);
 	++*pos;
 	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_f
 			entry_print->end,
 			cattr_name(entry_print->type));
 
-	kfree(entry_print);
-
 	return 0;
 }
 
_

Patches currently in -mm which might be from neilb@suse.de are

seq_file-document-how-per-entry-resources-are-managed.patch
x86-fix-seq_file-iteration-for-pat-memtypec.patch
net-fix-iteration-for-sctp-transport-seq_files.patch