Patchwork [Quantal] ext4: fix crash when accessing /proc/mounts concurrently

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Submitter Herton Ronaldo Krzesinski
Date Sept. 26, 2012, 1:35 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/187081/
State New
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Herton Ronaldo Krzesinski - Sept. 26, 2012, 1:35 p.m.
The crash was caused by a variable being erronously declared static in

In addition to /proc/mounts, the problem can also be easily replicated
by accessing /proc/fs/ext4/<partition>/options in parallel:

$ cat /proc/fs/ext4/<partition>/options > options.txt

... and then running the following command in two different terminals:

$ while diff /proc/fs/ext4/<partition>/options options.txt; do true; done

This is also the cause of the following a crash while running xfstests
#234, as reported in the following bug reports:

Signed-off-by: Herton Ronaldo Krzesinski <>
Signed-off-by: "Theodore Ts'o" <>
Cc: Brad Figg <>
(cherry picked from commit 04b6f64bf52bd6d0b8dcd912e8fec8d672d44d4a,
 at git:// dev)
 fs/ext4/super.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Tim Gardner - Sept. 26, 2012, 1:43 p.m.


diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index afeddd7..51d24ea 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1752,7 +1752,7 @@  static inline void ext4_show_quota_options(struct seq_file *seq,
 static const char *token2str(int token)
-	static const struct match_token *t;
+	const struct match_token *t;
 	for (t = tokens; t->token != Opt_err; t++)
 		if (t->token == token && !strchr(t->pattern, '='))