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On Thu, Dec 17, 2020 at 11:39 AM Patrick Donnelly <pdonnell@xxxxxxxxxx> wrote:
>
> On Wed, Dec 16, 2020 at 5:46 PM Alex Taylor <alexu4993@xxxxxxxxx> wrote:
> >
> > Hi Cephers,
> >
> > I'm using VSCode remote development with a docker server. It worked OK
> > but fails to start the debugger after /root mounted by ceph-fuse. The
> > log shows that the binary passes access X_OK check but cannot be
> > actually executed. see:
> >
> > ```
> > strace_log: access("/root/.vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7",
> > X_OK) = 0
> >
> > root@develop:~# ls -alh
> > .vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7
> > -rw-r--r-- 1 root root 978 Dec 10 13:06
> > .vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7
> > ```
> >
> > I also test the access syscall on ext4, xfs and even cephfs kernel
> > client, all of them return -EACCES, which is expected (the extension
> > will then explicitly call chmod +x).
> >
> > After some digging in the code, I found it is probably caused by
> > https://github.com/ceph/ceph/blob/master/src/client/Client.cc#L5549-L5550.
> > So here come two questions:
> > 1. Is this a bug or is there any concern I missed?
>
> I tried reproducing it with the master branch and could not. It might
> be due to an older fuse/ceph. I suggest you upgrade!
>
I tried the master(332a188d9b3c4eb5c5ad2720b7299913c5a772ee) as well
and the issue still exists. My test program is:
```
#include <stdio.h>
#include <unistd.h>
int main() {
int r;
const char path[] = "test";
r = access(path, F_OK);
printf("file exists: %d\n", r);
r = access(path, X_OK);
printf("file executable: %d\n", r);
return 0;
}
```
And the test result:
```
# local filesystem: ext4
root@f626800a6e85:~# ls -l test
-rw-r--r-- 1 root root 6 Dec 19 06:13 test
root@f626800a6e85:~# ./a.out
file exists: 0
file executable: -1
root@f626800a6e85:~# findmnt -t fuse.ceph-fuse
TARGET SOURCE FSTYPE OPTIONS
/root/mnt ceph-fuse fuse.ceph-fuse
rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other
root@f626800a6e85:~# cd mnt
# ceph-fuse
root@f626800a6e85:~/mnt# ls -l test
-rw-r--r-- 1 root root 6 Dec 19 06:10 test
root@f626800a6e85:~/mnt# ./a.out
file exists: 0
file executable: 0
root@f626800a6e85:~/mnt# ./test
bash: ./test: Permission denied
```
Again, ceph-fuse says file `test` is executable but in fact it can't
be executed.
The kernel version I'm testing on is:
```
root@f626800a6e85:~/mnt# uname -ar
Linux f626800a6e85 4.9.0-7-amd64 #1 SMP Debian 4.9.110-1 (2018-07-05)
x86_64 GNU/Linux
```
Please try the program above and make sure you're running it as root
user, thank you. And if the reproduction still fails, please let me
know the kernel version.
> > 2. It works again with fuse_default_permissions=true, any drawbacks if
> > this option is set?
>
> Correctness (ironically, for you) and performance.
>
> --
> Patrick Donnelly, Ph.D.
> He / Him / His
> Principal Software Engineer
> Red Hat Sunnyvale, CA
> GPG: 19F28A586F808C2402351B93C3301A3E258DD79D
>
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