svn commit: r367927 - in head: sys/kern tests/sys/kern

[Kyle Evans]

On Sun, Nov 22, 2020 at 11:25 AM Kyle Evans <kevans at freebsd.org> wrote:
>
> On Sun, Nov 22, 2020 at 10:36 AM Kyle Evans <kevans at freebsd.org> wrote:
> >
> > On Sun, Nov 22, 2020 at 9:54 AM Guy Yur <guyyur at gmail.com> wrote:
> > >
> > > On 22/11/20 7:00 am, Robert Wing wrote:
> > > > Author: rew
> > > > Date: Sun Nov 22 05:00:28 2020
> > > > New Revision: 367927
> > > > URL: https://svnweb.freebsd.org/changeset/base/367927
> > > >
> > > > Log:
> > > >    fd: free old file descriptor tables when not shared
> > > >
> > > >    During the life of a process, new file descriptor tables may be allocated. When
> > > >    a new table is allocated, the old table is placed in a free list and held onto
> > > >    until all processes referencing them exit.
> > > >
> > > >    When a new file descriptor table is allocated, the old file descriptor table
> > > >    can be freed when the current process has a single-thread and the file
> > > >    descriptor table is not being shared with any other processes.
> > > >
> > > >    Reviewed by:    kevans
> > > >    Approved by:    kevans (mentor)
> > > >    Differential Revision:  https://reviews.freebsd.org/D18617
> > > >
> > > > Added:
> > > >    head/tests/sys/kern/fdgrowtable_test.c   (contents, props changed)
> > > > Modified:
> > > >    head/sys/kern/kern_descrip.c
> > > >    head/tests/sys/kern/Makefile
> > >
> > > Hi,
> > >
> > > I am getting a kernel panic with this commit when building
> > > devel/gmake port and it runs dup2 test in configure script.
> > >
> > > panic: fc_ioctls != NULL, but fc_nioctls=-16162
> > > ...
> > > #10 0xffffffff80655c72 in vpanic (fmt=<optimized out>, ap=<optimized out>)
> > >      at /usr/src/sys/kern/kern_shutdown.c:907
> > > #11 0xffffffff80655a03 in panic (
> > >      fmt=0xffffffff80eb2b78 <cnputs_mtx> "헝\200\377\377\377\377")
> > >      at /usr/src/sys/kern/kern_shutdown.c:843
> > > #12 0xffffffff805fff9a in filecaps_copy_prep (src=<optimized out>)
> > >      at /usr/src/sys/kern/kern_descrip.c:1629
> > > #13 kern_dup (td=<optimized out>, mode=<optimized out>, flags=0,
> > >      old=<optimized out>, new=256) at /usr/src/sys/kern/kern_descrip.c:970
> > > #14 0xffffffff8094a5de in syscallenter (td=<optimized out>)
> > >      at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:189
> > > #15 amd64_syscall (td=0xfffffe00513f8500, traced=0)
> > >      at /usr/src/sys/amd64/amd64/trap.c:1156
> > >
> > >
> > > Simplified test program that causes panic:
> > > #include <unistd.h>
> > > #include <limits.h>
> > >
> > > int main ()
> > > {
> > >    int bad_fd = INT_MAX;
> > >    dup2 (1, 1);
> > >    close (0);
> > >    dup2 (0, 0);
> > >    dup2 (2, bad_fd);
> > >    dup2 (2, -1);
> > >    dup2 (2, 255);
> > >    dup2 (2, 256);
> > >    return 0;
> > > }
> > >
> >
> > Whoops. =\
> >
> > It looks like kern_dup grows the file table but assumes that it can
> > continue using oldfe that it fetched from the now-freed table. I
> > suspect we just need to refetch oldfde after the grow operation, and
> > it might be a good idea (under INVARIANTS) to grab the fp from oldfde
> > before we grow the table and assert that the new entry we fetch is the
> > same underlying file.
> >
>
> I can confirm that the below fixes it and no other growth spots keep
> pointers into the old table around, I'll give it a little bit for any
> objections to be raised then commit.
>

Bah, sorry, this still isn't right. The other paths may grow the table
via fdalloc(). I'll throw up a review for this shortly.