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authorMacpaul Lin <macpaul@gmail.com>2018-10-17 23:08:38 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-12-06 15:59:07 +0100
commitdada6a43b0402eba438a17ac86fdc64ac56a4607 (patch)
tree64d8b547d5a4a6a503cd141d68435c9206acf060
parent100bc3e2bebf95506da57cbdf5f26b25f6da4c81 (diff)
kgdboc: fix KASAN global-out-of-bounds bug in param_set_kgdboc_var()
This patch is trying to fix KE issue due to "BUG: KASAN: global-out-of-bounds in param_set_kgdboc_var+0x194/0x198" reported by Syzkaller scan." [26364:syz-executor0][name:report8t]BUG: KASAN: global-out-of-bounds in param_set_kgdboc_var+0x194/0x198 [26364:syz-executor0][name:report&]Read of size 1 at addr ffffff900e44f95f by task syz-executor0/26364 [26364:syz-executor0][name:report&] [26364:syz-executor0]CPU: 7 PID: 26364 Comm: syz-executor0 Tainted: G W 0 [26364:syz-executor0]Call trace: [26364:syz-executor0][<ffffff9008095cf8>] dump_bacIctrace+Ox0/0x470 [26364:syz-executor0][<ffffff9008096de0>] show_stack+0x20/0x30 [26364:syz-executor0][<ffffff90089cc9c8>] dump_stack+Oxd8/0x128 [26364:syz-executor0][<ffffff90084edb38>] print_address_description +0x80/0x4a8 [26364:syz-executor0][<ffffff90084ee270>] kasan_report+Ox178/0x390 [26364:syz-executor0][<ffffff90084ee4a0>] _asan_report_loadi_noabort+Ox18/0x20 [26364:syz-executor0][<ffffff9008b092ac>] param_set_kgdboc_var+Ox194/0x198 [26364:syz-executor0][<ffffff900813af64>] param_attr_store+Ox14c/0x270 [26364:syz-executor0][<ffffff90081394c8>] module_attr_store+0x60/0x90 [26364:syz-executor0][<ffffff90086690c0>] sysfs_kl_write+Ox100/0x158 [26364:syz-executor0][<ffffff9008666d84>] kernfs_fop_write+0x27c/0x3a8 [26364:syz-executor0][<ffffff9008508264>] do_loop_readv_writev+0x114/0x1b0 [26364:syz-executor0][<ffffff9008509ac8>] do_readv_writev+0x4f8/0x5e0 [26364:syz-executor0][<ffffff9008509ce4>] vfs_writev+0x7c/Oxb8 [26364:syz-executor0][<ffffff900850ba64>] SyS_writev+Oxcc/0x208 [26364:syz-executor0][<ffffff90080883f0>] elO_svc_naked +0x24/0x28 [26364:syz-executor0][name:report&] [26364:syz-executor0][name:report&]The buggy address belongs to the variable: [26364:syz-executor0][name:report&] kgdb_tty_line+Ox3f/0x40 [26364:syz-executor0][name:report&] [26364:syz-executor0][name:report&]Memory state around the buggy address: [26364:syz-executor0] ffffff900e44f800: 00 00 00 00 00 04 fa fa fa fa fa fa 00 fa fa fa [26364:syz-executor0] ffffff900e44f880: fa fa fa fa 00 fa fa fa fa fa fa fa 00 fa fa fa [26364:syz-executor0]> ffffff900e44f900: fa fa fa fa 04 fa fa fa fa fa fa fa 00 00 00 00 [26364:syz-executor0][name:report&] ^ [26364:syz-executor0] ffffff900e44f980: 00 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa [26364:syz-executor0] ffffff900e44fa00: 04 fa fa fa fa fa fa fa 00 fa fa fa fa fa fa fa [26364:syz-executor0][name:report&] [26364:syz-executor0][name:panic&]Disabling lock debugging due to kernel taint [26364:syz-executor0]------------[cut here]------------ After checking the source code, we've found there might be an out-of-bounds access to "config[len - 1]" array when the variable "len" is zero. Signed-off-by: Macpaul Lin <macpaul@gmail.com> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/kgdboc.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index baeeeaec3f03..6fb312e7af71 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -233,7 +233,7 @@ static void kgdboc_put_char(u8 chr)
static int param_set_kgdboc_var(const char *kmessage,
const struct kernel_param *kp)
{
- int len = strlen(kmessage);
+ size_t len = strlen(kmessage);
if (len >= MAX_CONFIG_LEN) {
pr_err("config string too long\n");
@@ -254,7 +254,7 @@ static int param_set_kgdboc_var(const char *kmessage,
strcpy(config, kmessage);
/* Chop out \n char as a result of echo */
- if (config[len - 1] == '\n')
+ if (len && config[len - 1] == '\n')
config[len - 1] = '\0';
if (configured == 1)