* User-triggerable WARNING with fuse
@ 2013-02-01 11:39 Tero Roponen
2013-02-04 14:56 ` Miklos Szeredi
0 siblings, 1 reply; 3+ messages in thread
From: Tero Roponen @ 2013-02-01 11:39 UTC (permalink / raw)
To: miklos; +Cc: fuse-devel, linux-kernel
[-- Attachment #1: Type: TEXT/PLAIN, Size: 1765 bytes --]
Using the attached program I can trigger the following WARNING
reliably as a normal user. This happens at least both in 3.8-rc6
and 3.7.5.
The kernel is tainted by proprietary NVIDIA module, but I don't
thinks it matters in this case.
[ 4390.882323] ------------[ cut here ]------------
[ 4390.882342] WARNING: at fs/inode.c:280 drop_nlink+0x41/0x50()
[ 4390.882345] Hardware name: M50Vm
[ 4390.882347] Modules linked in: fuse rfcomm bnep snd_hda_codec_hdmi
nvidia(PO) snd_hda_codec_realtek snd_hda_intel iwldvm snd_hda_codec
snd_hwdep uvcvideo btusb videobuf2_vmalloc videobuf2_memops videobuf2_core
mac80211 bluetooth snd_seq snd_seq_device snd_pcm asus_laptop iwlwifi
cfg80211 snd_page_alloc snd_timer videodev r8169 input_polldev
sparse_keymap snd soundcore kvm_intel kvm microcode rfkill i2c_core mii
pcspkr uinput hid_generic firewire_ohci sdhci_pci sdhci mmc_core
firewire_core crc_itu_t
[ 4390.882438] Pid: 6040, comm: rm Tainted: P W O 3.8.0-rc6 #1
[ 4390.882442] Call Trace:
[ 4390.882453] [<ffffffff81032eca>] warn_slowpath_common+0x7a/0xb0
[ 4390.882460] [<ffffffff81032f15>] warn_slowpath_null+0x15/0x20
[ 4390.882466] [<ffffffff81101dd1>] drop_nlink+0x41/0x50
[ 4390.882478] [<ffffffffa00d261f>] fuse_unlink+0xdf/0x130 [fuse]
[ 4390.882486] [<ffffffff810f6cfd>] vfs_unlink+0x8d/0x100
[ 4390.882493] [<ffffffff810f6f09>] do_unlinkat+0x199/0x220
[ 4390.882501] [<ffffffff81092e82>] ? call_rcu_sched+0x12/0x20
[ 4390.882508] [<ffffffff81057c2a>] ? __put_cred+0x3a/0x50
[ 4390.882516] [<ffffffff810e9977>] ? sys_faccessat+0x137/0x1e0
[ 4390.882524] [<ffffffff810f94b6>] sys_unlinkat+0x16/0x40
[ 4390.882532] [<ffffffff81490c16>] system_call_fastpath+0x1a/0x1f
[ 4390.882536] ---[ end trace 372eef394febff4c ]---
[-- Attachment #2: Type: TEXT/plain, Size: 830 bytes --]
/*
* $ gcc warn.c -o warn -D_FILE_OFFSET_BITS=64 -DFUSE_USE_VERSION=26 -lfuse
*
* $ mkdir mnt
* $ ./warn mnt
* $ rm mnt/foo
*/
#include <fuse/fuse.h>
static int readdir_op(const char *path, void *buf,
fuse_fill_dir_t filler, off_t offset,
struct fuse_file_info *fi)
{
struct stat st = {.st_mode = S_IFREG | 0666};
filler(buf, "foo", &st, 0);
return 0;
}
static int getattr_op(const char *path, struct stat *st)
{
if (strcmp(path, "/") == 0)
st->st_mode = S_IFDIR | 0777;
else
st->st_mode = S_IFREG | 0666;
return 0;
}
static int unlink_op(const char *path)
{
return 0;
}
static struct fuse_operations ops = {
.readdir = readdir_op,
.getattr = getattr_op,
.unlink = unlink_op,
};
int main(int argc, char *argv[])
{
return fuse_main(argc, argv, &ops, NULL);
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: User-triggerable WARNING with fuse
2013-02-01 11:39 User-triggerable WARNING with fuse Tero Roponen
@ 2013-02-04 14:56 ` Miklos Szeredi
2013-02-05 6:14 ` Tero Roponen
0 siblings, 1 reply; 3+ messages in thread
From: Miklos Szeredi @ 2013-02-04 14:56 UTC (permalink / raw)
To: Tero Roponen; +Cc: fuse-devel, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 380 bytes --]
On Fri, Feb 1, 2013 at 12:39 PM, Tero Roponen <tero.roponen@gmail.com> wrote:
>
> Using the attached program I can trigger the following WARNING
> reliably as a normal user. This happens at least both in 3.8-rc6
> and 3.7.5.
>
> The kernel is tainted by proprietary NVIDIA module, but I don't
> thinks it matters in this case.
>
Thanks, the attached patch should fix it.
Miklos
[-- Attachment #2: fuse-dont-warn-when-nlink-is-zero.patch --]
[-- Type: application/octet-stream, Size: 1004 bytes --]
From: Miklos Szeredi <mszeredi@suse.cz>
Subject: fuse: don't WARN when nlink is zero
drop_nlink() warns if nlink is already zero. This is triggerable by a buggy
userspace filesystem. The cure, I think, is worse than the disease so disable
the warning.
Reported-by: Tero Roponen <tero.roponen@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/fuse/dir.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -705,7 +705,14 @@ static int fuse_unlink(struct inode *dir
spin_lock(&fc->lock);
fi->attr_version = ++fc->attr_version;
- drop_nlink(inode);
+ /*
+ * If i_nlink == 0 then unlink doesn't make sense, yet this can
+ * happen if userspace filesystem is careless. It would be
+ * difficult to enforce correct nlink usage so just ignore this
+ * condition here
+ */
+ if (inode->i_nlink > 0)
+ drop_nlink(inode);
spin_unlock(&fc->lock);
fuse_invalidate_attr(inode);
fuse_invalidate_attr(dir);
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: User-triggerable WARNING with fuse
2013-02-04 14:56 ` Miklos Szeredi
@ 2013-02-05 6:14 ` Tero Roponen
0 siblings, 0 replies; 3+ messages in thread
From: Tero Roponen @ 2013-02-05 6:14 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: Tero Roponen, fuse-devel, linux-kernel
On Mon, 4 Feb 2013, Miklos Szeredi wrote:
> On Fri, Feb 1, 2013 at 12:39 PM, Tero Roponen <tero.roponen@gmail.com> wrote:
> >
> > Using the attached program I can trigger the following WARNING
> > reliably as a normal user. This happens at least both in 3.8-rc6
> > and 3.7.5.
> >
> > The kernel is tainted by proprietary NVIDIA module, but I don't
> > thinks it matters in this case.
> >
>
> Thanks, the attached patch should fix it.
Yes, that fixed it.
--
Tero Roponen
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-02-01 11:39 User-triggerable WARNING with fuse Tero Roponen
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