]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
sysfs: make sure read buffer is zeroed
authorTejun Heo <tj@kernel.org>
Mon, 19 May 2014 19:52:10 +0000 (15:52 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 20 May 2014 01:15:53 +0000 (10:15 +0900)
commitf5c16f29bf5e57ba4051fc7785ba7f035f798c71
treec7dadc302a01d7837ffb437a0d46618111aaf3a9
parent555724a831b4a146e7bdf16ecc989cda032b076d
sysfs: make sure read buffer is zeroed

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")
Cc: stable <stable@vger.kernel.org> # 3.13+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/sysfs/file.c