summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorTejun Heo <tj@kernel.org>2014-05-19 15:52:10 -0400
committerMaciej Wereski <m.wereski@partner.samsung.com>2015-06-09 11:31:20 +0200
commitd1866567499505b9f142f3073e95287db6cf36c2 (patch)
treed9cddbe227ca2268cbc1fed69ea56f7f6d49e343
parent5655d13b31921f30217d793d02f7c7ef8c5fcaf1 (diff)
downloadlinux-3.10-d1866567499505b9f142f3073e95287db6cf36c2.tar.gz
linux-3.10-d1866567499505b9f142f3073e95287db6cf36c2.tar.bz2
linux-3.10-d1866567499505b9f142f3073e95287db6cf36c2.zip
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>
-rw-r--r--fs/sysfs/file.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index a67d1c682fe..a7a188c3ed5 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