Greg KH <greg@xxxxxxxxx> writes: > On Mon, Oct 31, 2016 at 09:19:03PM +0100, Nicolai Stange wrote: >> Hi, >> >> Greg KH <greg@xxxxxxxxx> writes: >> >> > On Mon, Oct 31, 2016 at 02:32:56PM -0400, Mike Marshall wrote: >> >> > >> > [adding Nicolai to thread...] >> > >> >> >> >> >> Our debugfs code results in three files in /sys/kernel/debug/orangefs. >> >> One of the files gets deleted (debugfs_remove'd) and re-created >> >> (debugfs_create_file'd) the first time someone fires up the >> >> user-space part of Orangefs after a reboot. >> >> >> >> We wondered what awful things might happen if someone was >> >> reading the file across the delete/re-create, so I wrote a >> >> program that opens the file, sleeps ten seconds and then >> >> starts reading, and I fired up the Orangefs userspace part >> >> during the sleep. I didn't see any problems there, we get >> >> EIO when the read happens. >> >> >> >> But... really bad things happen if someone unloads the Orangefs >> >> module after my test program does the open and before the read >> >> starts. So I picked another debugfs-using-filesystem (f2fs) and >> >> pointed my tester-program at /sys/kernel/debug/f2fs/status, and >> >> the same bad thing happens there. >> >> [...] >> >> >> [ 1240.144316] Call Trace: >> >> [ 1240.144450] [<ffffffff8122907f>] __fput+0xdf/0x1d0 >> >> [ 1240.144704] [<ffffffff812291ae>] ____fput+0xe/0x10 >> >> [ 1240.144962] [<ffffffff810b97de>] task_work_run+0x8e/0xc0 >> >> [ 1240.145243] [<ffffffff8109b98e>] do_exit+0x2ae/0xae0 >> >> >> Thank you very much for this detailed report! >> >> At least for the .../f2fs/status file, your splat at fput() can be >> readily explained with the full proxy's releaser not being protected >> against file removals in any way. >> >> Partly this is on purpose, c.f. the comment in full_proxy_release(). >> >> However, I should have at least tried to acquire a reference to the >> owning module before accessing some static struct file_operations or >> even calling some ->release() within it. Meh. >> >> The fix should be relatively trivial and I'll hopefully manage to >> submit a patch tomorrow. >> >> May I add your (Mike Marshall's?) Reported-by? > > Did this patch ever show up? Not yet, sorry. I still have this on my list though and will definitely be able to find some free time this weekend. I hope this is Ok. Thanks, Nicolai -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
