On Sat, 24 Sep 2005, Nishanth Aravamudan wrote:
Description: The @timeout parameter to ep_poll() is in milliseconds but
we compare it to (MAX_SCHEDULE_TIMEOUT - 1000 / HZ), which is
(jiffies/jiffies-per-sec) or seconds. That seems blatantly broken. This
led to improper overflow checking for @timeout. As Andrew Morton pointed
out in a similar fix for sys_poll(), the best solution is to to check
for potential overflow first, then either select an indefinite value or
convert @timeout.
To achieve this and clean-up the code, change the prototype of the
ep_poll() to make it clear that the parameter is in milliseconds and
rename jtimeout to timeout_jiffies to hold the corresonding jiffies
value.
fs/eventpoll.c | 46 ++++++++++++++++++++++++++++++++++++++--------
1 files changed, 38 insertions(+), 8 deletions(-)
Eh? "To achieve this and clean-up the code"? :)
- Davide
eventpoll.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/fs/eventpoll.c 2005-09-24 11:07:04.000000000 -0700
+++ b/fs/eventpoll.c 2005-09-24 11:11:06.000000000 -0700
@@ -101,6 +101,10 @@
/* Maximum number of poll wake up nests we are allowing */
#define EP_MAX_POLLWAKE_NESTS 4
+/* Maximum msec timeout value storeable in a long int */
+#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, LONG_MAX / HZ - 1000ULL)
+
+
struct epoll_filefd {
struct file *file;
int fd;
@@ -1507,8 +1511,7 @@
* and the overflow condition. The passed timeout is in milliseconds,
* that why (t * HZ) / 1000.
*/
- jtimeout = (timeout < 0 ||
- (timeout / 1000) >= (MAX_SCHEDULE_TIMEOUT / HZ)) ?
+ jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ?
MAX_SCHEDULE_TIMEOUT: (timeout * HZ + 999) / 1000;
retry:
-
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