On Thu, Jul 26, 2001 at 08:54:48PM +0100, Alex Bligh - linux-kernel wrote:
> May be I'm being dumb here, and without wishing to open the 'volatile'
> can of worms elsewhere, but:
>
> static char * tmp_buf;
Here is the fix... I've updated it a bit to plug another small race in
rs_write as well.
The following code uses the tmp_buf_sem to lock the creation and freeing
of the tmp_buf page. This same lock is used to prevent concurrent accesses
to this very same page in rs_write().
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html
--- orig/drivers/char/serial.c Sat Jul 21 10:46:42 2001
+++ linux/drivers/char/serial.c Thu Jul 26 21:14:12 2001
@@ -1848,12 +1848,17 @@
if (serial_paranoia_check(info, tty->device, "rs_write"))
return 0;
- if (!tty || !info->xmit.buf || !tmp_buf)
+ if (!tty || !info->xmit.buf)
return 0;
save_flags(flags);
if (from_user) {
down(&tmp_buf_sem);
+ if (!tmp_buf) {
+ up(&tmp_buf_sem);
+ restore_flags(flags);
+ return 0;
+ }
while (1) {
int c1;
c = CIRC_SPACE_TO_END(info->xmit.head,
@@ -3129,7 +3134,6 @@
{
struct async_struct *info;
int retval, line;
- unsigned long page;
MOD_INC_USE_COUNT;
line = MINOR(tty->device) - tty->driver.minor_start;
@@ -3157,17 +3161,16 @@
info->tty->low_latency = (info->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
#endif
+ down(&tmp_buf_sem);
if (!tmp_buf) {
- page = get_zeroed_page(GFP_KERNEL);
- if (!page) {
+ tmp_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+ if (!tmp_buf) {
+ up(&tmp_buf_sem);
MOD_DEC_USE_COUNT;
return -ENOMEM;
}
- if (tmp_buf)
- free_page(page);
- else
- tmp_buf = (unsigned char *) page;
}
+ up(&tmp_buf_sem);
/*
* If the port is the middle of closing, bail out now
@@ -5666,12 +5669,13 @@
if (DEACTIVATE_FUNC(brd->dev))
(DEACTIVATE_FUNC(brd->dev))(brd->dev);
}
-#endif
+#endif
+ down(&tmp_buf_sem);
if (tmp_buf) {
- unsigned long pg = (unsigned long) tmp_buf;
+ free_page(tmp_buf);
tmp_buf = NULL;
- free_page(pg);
}
+ up(&tmp_buf_sem);
#ifdef ENABLE_SERIAL_PCI
if (serial_pci_driver.name[0])
-
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This archive was generated by hypermail 2b29 : Tue Jul 31 2001 - 21:00:29 EST