From 098284020c47c1212d211e39ae2b41c21182e056 Mon Sep 17 00:00:00 2001 From: Davide Libenzi Date: Thu, 26 Jul 2007 10:41:07 -0700 Subject: [PATCH] make timerfd return a u64 and fix the __put_user Davi fixed a missing cast in the __put_user(), that was making timerfd return a single byte instead of the full value. Talking with Michael about the timerfd man page, we think it'd be better to use a u64 for the returned value, to align it with the eventfd implementation. This is an ABI change. The timerfd code is new in 2.6.22 and if we merge this into 2.6.23 then we should also merge it into 2.6.22.x. That will leave a few early 2.6.22 kernels out in the wild which might misbehave when a future timerfd-enabled glibc is run on them. mtk says: The difference would be that read() will only return 4 bytes, while the application will expect 8. If the application is checking the size of returned value, as it should, then it will be able to detect the problem (it could even be sophisticated enough to know that if this is a 4-byte return, then it is running on an old 2.6.22 kernel). If the application is not checking the return from read(), then its 8-byte buffer will not be filled -- the contents of the last 4 bytes will be undefined, so the u64 value as a whole will be junk. Signed-off-by: Davide Libenzi Cc: Michael Kerrisk Cc: Davi Arnaut Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/timerfd.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/timerfd.c b/fs/timerfd.c index af9eca5c023..61983f3b107 100644 --- a/fs/timerfd.c +++ b/fs/timerfd.c @@ -95,7 +95,7 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, { struct timerfd_ctx *ctx = file->private_data; ssize_t res; - u32 ticks = 0; + u64 ticks = 0; DECLARE_WAITQUEUE(wait, current); if (count < sizeof(ticks)) @@ -130,7 +130,7 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, * callback to avoid DoS attacks specifying a very * short timer period. */ - ticks = (u32) + ticks = (u64) hrtimer_forward(&ctx->tmr, hrtimer_cb_get_time(&ctx->tmr), ctx->tintv); @@ -140,7 +140,7 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, } spin_unlock_irq(&ctx->wqh.lock); if (ticks) - res = put_user(ticks, buf) ? -EFAULT: sizeof(ticks); + res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); return res; } -- 2.41.1