From f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Sun, 8 May 2022 11:37:07 +0200
Subject: [PATCH] floppy: use a statically allocated error counter
Git-commit: f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8
Patch-mainline: v5.18-rc6
References: bsc#1199063 CVE-2022-1652
Interrupt handler bad_flp_intr() may cause a UAF on the recently freed
request just to increment the error count. There's no point keeping
that one in the request anyway, and since the interrupt handler uses a
static pointer to the error which cannot be kept in sync with the
pending request, better make it use a static error counter that's reset
for each new request. This reset now happens when entering
redo_fd_request() for a new request via set_next_request().
One initial concern about a single error counter was that errors on one
floppy drive could be reported on another one, but this problem is not
real given that the driver uses a single drive at a time, as that
PC-compatible controllers also have this limitation by using shared
signals. As such the error count is always for the "current" drive.
Reported-by: Minh Yuan <yuanmingbuaa@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Tested-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Denis Efremov <efremov@linux.com>
Acked-by: Petr Mladek <pmladek@suse.com>
[ pmladek@suse.com:
Backported for 4.19 by Denis Efremov <efremov@linux.com>, see
https://lore.kernel.org/all/20220517203516.60030-1-efremov@linux.com/
]
---
drivers/block/floppy.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 97c8fc4d6e7b..0e66314415c5 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -520,8 +520,8 @@ static unsigned long fdc_busy;
static DECLARE_WAIT_QUEUE_HEAD(fdc_wait);
static DECLARE_WAIT_QUEUE_HEAD(command_done);
-/* Errors during formatting are counted here. */
-static int format_errors;
+/* errors encountered on the current (or last) request */
+static int floppy_errors;
/* Format request descriptor. */
static struct format_descr format_req;
@@ -541,7 +541,6 @@ static struct format_descr format_req;
static char *floppy_track_buffer;
static int max_buffer_sectors;
-static int *errors;
typedef void (*done_f)(int);
static const struct cont_t {
void (*interrupt)(void);
@@ -1434,7 +1433,7 @@ static int interpret_errors(void)
if (DP->flags & FTD_MSG)
DPRINT("Over/Underrun - retrying\n");
bad = 0;
- } else if (*errors >= DP->max_errors.reporting) {
+ } else if (floppy_errors >= DP->max_errors.reporting) {
print_errors();
}
if (ST2 & ST2_WC || ST2 & ST2_BC)
@@ -2054,7 +2053,7 @@ static void bad_flp_intr(void)
if (!next_valid_format())
return;
}
- err_count = ++(*errors);
+ err_count = ++floppy_errors;
INFBOUND(DRWE->badness, err_count);
if (err_count > DP->max_errors.abort)
cont->done(0);
@@ -2199,9 +2198,8 @@ static int do_format(int drive, struct format_descr *tmp_format_req)
return -EINVAL;
}
format_req = *tmp_format_req;
- format_errors = 0;
cont = &format_cont;
- errors = &format_errors;
+ floppy_errors = 0;
ret = wait_til_done(redo_format, true);
if (ret == -EINTR)
return -EINTR;
@@ -2684,7 +2682,7 @@ static int make_raw_rw_request(void)
*/
if (!direct ||
(indirect * 2 > direct * 3 &&
- *errors < DP->max_errors.read_track &&
+ floppy_errors < DP->max_errors.read_track &&
((!probing ||
(DP->read_track & (1 << DRS->probed_format)))))) {
max_size = blk_rq_sectors(current_req);
@@ -2818,7 +2816,7 @@ static int set_next_request(void)
if (q) {
current_req = blk_fetch_request(q);
if (current_req) {
- current_req->error_count = 0;
+ floppy_errors = 0;
break;
}
}
@@ -2880,7 +2878,6 @@ static void redo_fd_request(void)
_floppy = floppy_type + DP->autodetect[DRS->probed_format];
} else
probing = 0;
- errors = &(current_req->error_count);
tmp = make_raw_rw_request();
if (tmp < 2) {
request_done(tmp);
--
2.35.3