github-mirror/lkmpg
github-mirror/lkmpg
2
0
Fork 0
mirror of https://github.com/sysprog21/lkmpg.git synced 2025-03-13 14:05:10 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

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

Browse Source 
Fix blocking O_NONBLOCK process bug
This commit is contained in:
Jim Huang 2024-08-12 09:34:04 +08:00 committed by GitHub
commit 47663d6aa1
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
examples/sleep.c
View File

@ -92,12 +92,18 @@ static DECLARE_WAIT_QUEUE_HEAD(waitq);
/* Called when the /proc file is opened */ /* Called when the /proc file is opened */
static int module_open(struct inode *inode, struct file *file) 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 /* 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", * we should fail with -EAGAIN, meaning "you will have to try again",
* instead of blocking a process which would rather stay awake. * 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; return -EAGAIN;
/* This is the correct place for try_module_get(THIS_MODULE) because if /* This is the correct place for try_module_get(THIS_MODULE) because if