On Sun, Nov 22, 2020 at 10:36 AM Kyle Evans <kev...@freebsd.org> wrote:
>
> On Sun, Nov 22, 2020 at 9:54 AM Guy Yur <guy...@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.
diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index b5680bd79e1..1a3a5cafbea 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -936,6 +936,12 @@ kern_dup(struct thread *td, u_int mode, int
flags, int old, int new)
break;
case FDDUP_FIXED:
if (new >= fdp->fd_nfiles) {
+#ifdef INVARIANTS
+ struct file *ofp;
+
+ ofp = oldfde->fde_file;
+#endif
+
/*
* The resource limits are here instead of e.g.
* fdalloc(), because the file descriptor table may be
@@ -955,6 +961,11 @@ kern_dup(struct thread *td, u_int mode, int
flags, int old, int new)
}
#endif
fdgrowtable_exp(fdp, new + 1);
+ /* Refetch; old entry may be invalid. */
+ oldfde = &fdp->fd_ofiles[old];
+ KASSERT(ofp == oldfde->fde_file,
+ ("fdt_ofiles shift from growth observed at fd %d",
+ old));
}
if (!fdisused(fdp, new))
fdused(fdp, new);
_______________________________________________
svn-src-head@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
