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Merge pull request #266 from Ayxan13/fix-sleep-toctou

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Fix blocking O_NONBLOCK process bug
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Jim Huang 2024-08-12 09:34:04 +08:00 committed by GitHub
commit 47663d6aa1
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1 changed files with 8 additions and 2 deletions
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10
examples/sleep.c
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@ -92,12 +92,18 @@ static DECLARE_WAIT_QUEUE_HEAD(waitq);
/* Called when the /proc file is opened */
static int module_open(struct inode *inode, struct file *file)
{
/* Try to get without blocking */
if (!atomic_cmpxchg(&already_open, 0, 1)) {
/* Success without blocking, allow the access */
try_module_get(THIS_MODULE);
return 0;
}
/* If the file's flags include O_NONBLOCK, it means the process does not
* want to wait for the file. In this case, if the file is already open,
* want to wait for the file. In this case, because the file is already open,
* we should fail with -EAGAIN, meaning "you will have to try again",
* instead of blocking a process which would rather stay awake.
*/
if ((file->f_flags & O_NONBLOCK) && atomic_read(&already_open))
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
/* This is the correct place for try_module_get(THIS_MODULE) because if