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floppy: use a statically allocated error counter 

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>
This commit is contained in:
Willy Tarreau 2022-05-08 11:37:07 +02:00 committed by Linus Torvalds
parent 30c8e80f79
commit f71f01394f
1 changed files with 8 additions and 10 deletions
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18
drivers/block/floppy.c
View File

@ -509,8 +509,8 @@ 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;
@ -530,7 +530,6 @@ 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);
@ -1455,7 +1454,7 @@ static int interpret_errors(void)
if (drive_params[current_drive].flags & FTD_MSG)
DPRINT("Over/Underrun - retrying\n");
bad = 0;
} else if (*errors >= drive_params[current_drive].max_errors.reporting) {
} else if (floppy_errors >= drive_params[current_drive].max_errors.reporting) {
print_errors();
}
if (reply_buffer[ST2] & ST2_WC || reply_buffer[ST2] & ST2_BC)
@ -2095,7 +2094,7 @@ static void bad_flp_intr(void)
if (!next_valid_format(current_drive))
return;
}
err_count = ++(*errors);
err_count = ++floppy_errors;
INFBOUND(write_errors[current_drive].badness, err_count);
if (err_count > drive_params[current_drive].max_errors.abort)
cont->done(0);
@ -2241,9 +2240,8 @@ 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;
@ -2759,10 +2757,11 @@ static int set_next_request(void)
current_req = list_first_entry_or_null(&floppy_reqs, struct request,
queuelist);
if (current_req) {
current_req->error_count = 0;
floppy_errors = 0;
list_del_init(&current_req->queuelist);
return 1;
}
return current_req != NULL;
return 0;
}
/* Starts or continues processing request. Will automatically unlock the
@ -2821,7 +2820,6 @@ do_request:
_floppy = floppy_type + drive_params[current_drive].autodetect[drive_state[current_drive].probed_format];
} else
probing = 0;
errors = &(current_req->error_count);
tmp = make_raw_rw_request();
if (tmp < 2) {
request_done(tmp);