3.13.11.4 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Tejun Heo <[email protected]> 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 <[email protected]> Reported-by: Ron <[email protected]> Fixes: 13c589d5b0ac ("sysfs: use seq_file when reading regular files") Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- fs/sysfs/file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 35e7d08..ea3e7e2 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -94,12 +94,13 @@ static int sysfs_seq_show(struct seq_file *sf, void *v) char *buf; ssize_t count; - /* 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); /* * Need @of->sd for attr and ops, its parent for kobj. @of->mutex -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
