From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
syzbot <syzbot+18df353d7540aa6b5467@syzkaller.appspotmail.com>,
Peter Hurley <peter@hurleysoftware.com>
Subject: [PATCH 3.18 01/23] n_tty: Fix stall at n_tty_receive_char_special().
Date: Tue, 10 Jul 2018 20:24:34 +0200 [thread overview]
Message-ID: <20180710182308.933799891@linuxfoundation.org> (raw)
In-Reply-To: <20180710182308.877332304@linuxfoundation.org>
3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
commit 3d63b7e4ae0dc5e02d28ddd2fa1f945defc68d81 upstream.
syzbot is reporting stalls at n_tty_receive_char_special() [1]. This is
because comparison is not working as expected since ldata->read_head can
change at any moment. Mitigate this by explicitly masking with buffer size
when checking condition for "while" loops.
[1] https://syzkaller.appspot.com/bug?id=3d7481a346958d9469bebbeb0537d5f056bdd6e8
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+18df353d7540aa6b5467@syzkaller.appspotmail.com>
Fixes: bc5a5e3f45d04784 ("n_tty: Don't wrap input buffer indices at buffer size")
Cc: stable <stable@vger.kernel.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/n_tty.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -127,6 +127,8 @@ struct n_tty_data {
struct mutex output_lock;
};
+#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
+
static inline size_t read_cnt(struct n_tty_data *ldata)
{
return ldata->read_head - ldata->read_tail;
@@ -1032,14 +1034,15 @@ static void eraser(unsigned char c, stru
}
seen_alnums = 0;
- while (ldata->read_head != ldata->canon_head) {
+ while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
head = ldata->read_head;
/* erase a single possibly multibyte character */
do {
head--;
c = read_buf(ldata, head);
- } while (is_continuation(c, tty) && head != ldata->canon_head);
+ } while (is_continuation(c, tty) &&
+ MASK(head) != MASK(ldata->canon_head));
/* do not partially erase */
if (is_continuation(c, tty))
@@ -1081,7 +1084,7 @@ static void eraser(unsigned char c, stru
* This info is used to go back the correct
* number of columns.
*/
- while (tail != ldata->canon_head) {
+ while (MASK(tail) != MASK(ldata->canon_head)) {
tail--;
c = read_buf(ldata, tail);
if (c == '\t') {
@@ -1341,7 +1344,7 @@ n_tty_receive_char_special(struct tty_st
finish_erasing(ldata);
echo_char(c, tty);
echo_char_raw('\n', ldata);
- while (tail != ldata->read_head) {
+ while (MASK(tail) != MASK(ldata->read_head)) {
echo_char(read_buf(ldata, tail), tty);
tail++;
}
@@ -2505,7 +2508,7 @@ static unsigned long inq_canon(struct n_
tail = ldata->read_tail;
nr = head - tail;
/* Skip EOF-chars.. */
- while (head != tail) {
+ while (MASK(head) != MASK(tail)) {
if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
read_buf(ldata, tail) == __DISABLED_CHAR)
nr--;
next prev parent reply other threads:[~2018-07-10 18:25 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 18:24 [PATCH 3.18 00/23] 3.18.115-stable review Greg Kroah-Hartman
2018-07-10 18:24 ` Greg Kroah-Hartman [this message]
2018-07-10 18:24 ` [PATCH 3.18 02/23] staging: android: ion: Return an ERR_PTR in ion_map_kernel Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 03/23] x86/boot: Fix early command-line parsing when matching at end Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 04/23] ubi: fastmap: Correctly handle interrupted erasures in EBA Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 05/23] netfilter: ebtables: handle string from userspace with care Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 06/23] atm: zatm: fix memcmp casting Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 07/23] net: qmi_wwan: Add Netgear Aircard 779S Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 08/23] net/sonic: Use dma_mapping_error() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 09/23] scsi: sg: mitigate read/write abuse Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 10/23] cifs: Fix infinite loop when using hard mount option Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 11/23] ext4: make sure bitmaps and the inode table dont overlap with bg descriptors Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 12/23] ext4: clear i_data in ext4_inode_info when removing inline data Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 13/23] ext4: add more mount time checks of the superblock Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 14/23] HID: i2c-hid: Fix "incomplete report" noise Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 15/23] HID: debug: check length before copy_to_user() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 16/23] media: cx25840: Use subdev host data for PLL override Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 17/23] dm bufio: avoid sleeping while holding the dm_bufio lock Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 18/23] dm bufio: drop the lock when doing GFP_NOIO allocation Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 19/23] mtd: rawnand: mxc: set spare area size register explicitly Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 20/23] mtd: cfi_cmdset_0002: Change definition naming to retry write operation Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 21/23] mtd: cfi_cmdset_0002: Change erase functions to retry for error Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 22/23] mtd: cfi_cmdset_0002: Change erase functions to check chip good only Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 3.18 23/23] netfilter: nf_log: dont hold nf_log_mutex during user access Greg Kroah-Hartman
2018-07-10 19:09 ` [PATCH 3.18 00/23] 3.18.115-stable review Nathan Chancellor
2018-07-10 20:19 ` Harsh 'Shandilya
2018-07-11 11:05 ` Greg Kroah-Hartman
2018-07-11 13:39 ` Guenter Roeck
2018-07-11 15:10 ` Shuah Khan
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