uprobes cannot successfully attach to binaries located in a directory
mounted with overlayfs.
To verify, create directories for mounting overlayfs
(upper,lower,work,merge), move some binary into merge/ and use readelf
to obtain some known instruction of the binary. I used /bin/true and the
entry instruction(0x13b0):
$ mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merge
$ cd /sys/kernel/debug/tracing
$ echo 'p:true_entry PATH_TO_MERGE/merge/true:0x13b0' > uprobe_events
$ echo 1 > events/uprobes/true_entry/enable
This returns 'bash: echo: write error: Input/output error' and dmesg
tells us 'event trace: Could not enable event true_entry'
This change makes create_trace_uprobe() look for the real inode of a
dentry. In the case of normal filesystems, this simplifies to just
returning the inode. In the case of overlayfs(and similar fs) we will
obtain the underlying dentry and corresponding inode, upon which uprobes
can successfully register.
Running the example above with the patch applied, we can see that the
uprobe is enabled and will output to trace as expected.
Reviewed-by: Josef Bacik <[email protected]>
Signed-off-by: Howard McLauchlan <[email protected]>
---
kernel/trace/trace_uprobe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 2014f4351ae0..17c65fa4136d 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -446,7 +446,7 @@ static int create_trace_uprobe(int argc, char **argv)
if (ret)
goto fail_address_parse;
- inode = igrab(d_inode(path.dentry));
+ inode = igrab(d_real_inode(path.dentry));
path_put(&path);
if (!inode || !S_ISREG(inode->i_mode)) {
--
2.17.0
On Tue, 10 Apr 2018 16:10:30 -0700
Howard McLauchlan <[email protected]> wrote:
> uprobes cannot successfully attach to binaries located in a directory
> mounted with overlayfs.
>
> To verify, create directories for mounting overlayfs
> (upper,lower,work,merge), move some binary into merge/ and use readelf
> to obtain some known instruction of the binary. I used /bin/true and the
> entry instruction(0x13b0):
>
> $ mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merge
> $ cd /sys/kernel/debug/tracing
> $ echo 'p:true_entry PATH_TO_MERGE/merge/true:0x13b0' > uprobe_events
> $ echo 1 > events/uprobes/true_entry/enable
>
> This returns 'bash: echo: write error: Input/output error' and dmesg
> tells us 'event trace: Could not enable event true_entry'
I tried the above and verified that it is a problem and your patch
solves it.
Thanks, I'll apply it and start my tests on it.
-- Steve
>
> This change makes create_trace_uprobe() look for the real inode of a
> dentry. In the case of normal filesystems, this simplifies to just
> returning the inode. In the case of overlayfs(and similar fs) we will
> obtain the underlying dentry and corresponding inode, upon which uprobes
> can successfully register.
>
> Running the example above with the patch applied, we can see that the
> uprobe is enabled and will output to trace as expected.
>
> Reviewed-by: Josef Bacik <[email protected]>
> Signed-off-by: Howard McLauchlan <[email protected]>
> ---
> kernel/trace/trace_uprobe.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 2014f4351ae0..17c65fa4136d 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -446,7 +446,7 @@ static int create_trace_uprobe(int argc, char **argv)
> if (ret)
> goto fail_address_parse;
>
> - inode = igrab(d_inode(path.dentry));
> + inode = igrab(d_real_inode(path.dentry));
> path_put(&path);
>
> if (!inode || !S_ISREG(inode->i_mode)) {
On Tue, 10 Apr 2018 20:00:59 -0400
Steven Rostedt <[email protected]> wrote:
> On Tue, 10 Apr 2018 16:10:30 -0700
> Howard McLauchlan <[email protected]> wrote:
>
> > uprobes cannot successfully attach to binaries located in a directory
> > mounted with overlayfs.
> >
> > To verify, create directories for mounting overlayfs
> > (upper,lower,work,merge), move some binary into merge/ and use readelf
> > to obtain some known instruction of the binary. I used /bin/true and the
> > entry instruction(0x13b0):
> >
> > $ mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merge
> > $ cd /sys/kernel/debug/tracing
> > $ echo 'p:true_entry PATH_TO_MERGE/merge/true:0x13b0' > uprobe_events
> > $ echo 1 > events/uprobes/true_entry/enable
> >
> > This returns 'bash: echo: write error: Input/output error' and dmesg
> > tells us 'event trace: Could not enable event true_entry'
>
> I tried the above and verified that it is a problem and your patch
> solves it.
>
> Thanks, I'll apply it and start my tests on it.
This looks good to me.
Reviewed-by: Masami Hiramatsu <[email protected]>
Thanks!
>
> -- Steve
>
> >
> > This change makes create_trace_uprobe() look for the real inode of a
> > dentry. In the case of normal filesystems, this simplifies to just
> > returning the inode. In the case of overlayfs(and similar fs) we will
> > obtain the underlying dentry and corresponding inode, upon which uprobes
> > can successfully register.
> >
> > Running the example above with the patch applied, we can see that the
> > uprobe is enabled and will output to trace as expected.
> >
> > Reviewed-by: Josef Bacik <[email protected]>
> > Signed-off-by: Howard McLauchlan <[email protected]>
> > ---
> > kernel/trace/trace_uprobe.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> > index 2014f4351ae0..17c65fa4136d 100644
> > --- a/kernel/trace/trace_uprobe.c
> > +++ b/kernel/trace/trace_uprobe.c
> > @@ -446,7 +446,7 @@ static int create_trace_uprobe(int argc, char **argv)
> > if (ret)
> > goto fail_address_parse;
> >
> > - inode = igrab(d_inode(path.dentry));
> > + inode = igrab(d_real_inode(path.dentry));
> > path_put(&path);
> >
> > if (!inode || !S_ISREG(inode->i_mode)) {
>
--
Masami Hiramatsu <[email protected]>
* Steven Rostedt <[email protected]> [2018-04-10 20:00:59]:
> On Tue, 10 Apr 2018 16:10:30 -0700
> Howard McLauchlan <[email protected]> wrote:
>
> > uprobes cannot successfully attach to binaries located in a directory
> > mounted with overlayfs.
> >
> > To verify, create directories for mounting overlayfs
> > (upper,lower,work,merge), move some binary into merge/ and use readelf
> > to obtain some known instruction of the binary. I used /bin/true and the
> > entry instruction(0x13b0):
> >
> > $ mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merge
> > $ cd /sys/kernel/debug/tracing
> > $ echo 'p:true_entry PATH_TO_MERGE/merge/true:0x13b0' > uprobe_events
> > $ echo 1 > events/uprobes/true_entry/enable
> >
> > This returns 'bash: echo: write error: Input/output error' and dmesg
> > tells us 'event trace: Could not enable event true_entry'
>
> I tried the above and verified that it is a problem and your patch
> solves it.
>
> Thanks, I'll apply it and start my tests on it.
>
> -- Steve
>
> >
> > This change makes create_trace_uprobe() look for the real inode of a
> > dentry. In the case of normal filesystems, this simplifies to just
> > returning the inode. In the case of overlayfs(and similar fs) we will
> > obtain the underlying dentry and corresponding inode, upon which uprobes
> > can successfully register.
> >
> > Running the example above with the patch applied, we can see that the
> > uprobe is enabled and will output to trace as expected.
> >
Looks good to me.
Reviewed-by: Srikar Dronamraju <[email protected]>
> > Reviewed-by: Josef Bacik <[email protected]>
> > Signed-off-by: Howard McLauchlan <[email protected]>
> > ---
> > kernel/trace/trace_uprobe.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> > index 2014f4351ae0..17c65fa4136d 100644
> > --- a/kernel/trace/trace_uprobe.c
> > +++ b/kernel/trace/trace_uprobe.c
> > @@ -446,7 +446,7 @@ static int create_trace_uprobe(int argc, char **argv)
> > if (ret)
> > goto fail_address_parse;
> >
> > - inode = igrab(d_inode(path.dentry));
> > + inode = igrab(d_real_inode(path.dentry));
> > path_put(&path);
> >
> > if (!inode || !S_ISREG(inode->i_mode)) {
>