* [PATCH] statfs: fix potential Spectre v1
@ 2018-08-15 13:36 Gustavo A. R. Silva
0 siblings, 0 replies; only message in thread
From: Gustavo A. R. Silva @ 2018-08-15 13:36 UTC (permalink / raw)
To: Alexander Viro; +Cc: linux-fsdevel, linux-kernel, Gustavo A. R. Silva
user_params.request is indirectly controlled by user-space, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.
This issue was detected with the help of Smatch:
fs/statfs.c:908 __do_sys_fsinfo() warn: potential spectre issue
'fsinfo_buffer_sizes' [r]
Fix this by sanitizing user_params.request before using it to index
fsinfo_buffer_sizes
Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].
[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
fs/statfs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/statfs.c b/fs/statfs.c
index f714f05..d74a60a 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -11,6 +11,7 @@
#include <linux/compat.h>
#include <linux/fsinfo.h>
#include <linux/fs_parser.h>
+#include <linux/nospec.h>
#include "internal.h"
static int flags_by_mnt(int mnt_flags)
@@ -886,6 +887,8 @@ SYSCALL_DEFINE5(fsinfo,
return -EINVAL;
if (user_params.request >= FSINFO_ATTR__NR)
return -EOPNOTSUPP;
+ user_params.request = array_index_nospec(user_params.request,
+ FSINFO_ATTR__NR);
params.at_flags = user_params.at_flags;
params.request = user_params.request;
params.Nth = user_params.Nth;
--
2.7.4
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