[Bug 220035] [ufs] sys/ufs/ufs/ufs_vnops.c: a sleep-under-mutex bug in acl_alloc

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=220035

            Bug ID: 220035
           Summary: [ufs] sys/ufs/ufs/ufs_vnops.c: a sleep-under-mutex bug
                    in acl_alloc
           Product: Base System
           Version: 11.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: baijiaju1990 at 163.com

The ufs program may sleep under a mutex, and the code path in file
"sys/ufs/ufs/ufs_vnops.c" in FreeBSD 11.0 is:
ufs_accessx [line 363: acquire the mutex]
ufs_accessx [line 369]
ufs_accessx [line 372]
ufs_accessx [line 374]
ufs_accessx [line 376]
ufs_accessx [line 379]
ufs_accessx [line 383]
ufs_accessx [line 389]
ufs_accessx [line 394]
ufs_accessx [line 395]
ufs_accessx [line 398]
  acl_alloc(M_WAITOK) [line 400] --> may sleep

The possible fix of these bugs is to set the parameter in acl_alloc to
"M_NOWAIT".

This bug is found by a static analysis tool written by myself, and it is
checked by my review of the FreeBSD code.

By the way, I am a freshman in developing FreeBSD drivers, and I am willing to
submit a patch. But I do not know how to write and submit a patch, and where to
submit, so I am looking forward to useful advice :)

Jia-Ju Bai

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