diff options
| author | Tejun Heo <tj@kernel.org> | 2014-05-19 15:52:10 -0400 |
|---|---|---|
| committer | Show Liu <show.liu@linaro.org> | 2014-06-18 12:05:02 +0800 |
| commit | 88dfa94c331e00ff6bc557f24f84c5a46944b6cf (patch) | |
| tree | f4b0171fa12d615ec4aa1e27ed568e693f5b02a3 /fs | |
| parent | 7294c5f99dd1ab2646c945ada52e1c389052506a (diff) | |
sysfs: make sure read buffer is zeroed
commit f5c16f29bf5e57ba4051fc7785ba7f035f798c71 upstream.
13c589d5b0ac ("sysfs: use seq_file when reading regular files")
switched sysfs from custom read implementation to seq_file to enable
later transition to kernfs. After the change, the buffer passed to
->show() is acquired through seq_get_buf(); unfortunately, this
introduces a subtle behavior change. Before the commit, the buffer
passed to ->show() was always zero as it was allocated using
get_zeroed_page(). Because seq_file doesn't clear buffers on
allocation and neither does seq_get_buf(), after the commit, depending
on the behavior of ->show(), we may end up exposing uninitialized data
to userland thus possibly altering userland visible behavior and
leaking information.
Fix it by explicitly clearing the buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ron <ron@debian.org>
Fixes: 13c589d5b0ac ("sysfs: use seq_file when reading regular files")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/sysfs/file.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 810cf6e613e..5fd2bf18e27 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -47,12 +47,13 @@ static int sysfs_kf_seq_show(struct seq_file *sf, void *v) ssize_t count; char *buf; - /* acquire buffer and ensure that it's >= PAGE_SIZE */ + /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */ count = seq_get_buf(sf, &buf); if (count < PAGE_SIZE) { seq_commit(sf, -1); return 0; } + memset(buf, 0, PAGE_SIZE); /* * Invoke show(). Control may reach here via seq file lseek even |