[PATCH 1/1 v2] fanotify.7: BUGS, error handling in fanotify_read

[PATCH 1/1 v2] fanotify.7: BUGS, error handling in fanotify_read

[Heinrich Schuchardt]

The patch in
http://www.spinics.net/lists/linux-man/msg05589.html
was not accepted.

Michael Kerrisk suggested in a private mail to add a comment
in the BUGS section.

Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
---
 man7/fanotify.7 | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/man7/fanotify.7 b/man7/fanotify.7
index 2a92908..c6cec7c 100644
--- a/man7/fanotify.7
+++ b/man7/fanotify.7
@@ -164,7 +164,7 @@ so that multiple events can be retrieved by a single
 The return value of
 .BR read (2)
 is the number of bytes placed in the buffer,
-or \-1 in case of an error.
+or \-1 in case of an error (but see BUGS).
 
 The fields of the
 .I fanotify_event_metadata
@@ -468,7 +468,7 @@ The event queue can overflow.
 In this case, events are lost.
 .SH BUGS
 As of Linux 3.15,
-the following bug exists:
+the following bugs exists:
 .IP * 3
 .\" FIXME: A patch was proposed.
 When an event is generated,
@@ -478,6 +478,16 @@ before passing a file descriptor for that file.
 This poses a security risk, when the
 .B CAP_SYS_ADMIN
 capability is set for programs executed by unprivileged users.
+.IP *
+If a call to
+.BR read( 2 )
+processes multiple events from the fanotify queue and an error occurs, the
+return value will be the cumulated length of the events successfully copied to
+the user space buffer before the error occured.
+The return value will not be \-1.
+.I errno
+will not be set.
+Thus, the user program has no way to detect the error.
 .SH EXAMPLE
 The following program demonstrates the usage of the fanotify API.
 It marks the mount point passed as a command-line argument
-- 
2.0.0.rc0

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Re: [PATCH 1/1 v2] fanotify.7: BUGS, error handling in fanotify_read

[Michael Kerrisk (man-pages)]

[Expanded CC]

Jan, Eric,

Do you have any comments/additions for this man-pages patch?

Cheers,

Michael



On Wed, May 14, 2014 at 8:10 PM, Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org> wrote:
> The patch in
> http://www.spinics.net/lists/linux-man/msg05589.html
> was not accepted.
>
> Michael Kerrisk suggested in a private mail to add a comment
> in the BUGS section.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
> ---
>  man7/fanotify.7 | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/man7/fanotify.7 b/man7/fanotify.7
> index 2a92908..c6cec7c 100644
> --- a/man7/fanotify.7
> +++ b/man7/fanotify.7
> @@ -164,7 +164,7 @@ so that multiple events can be retrieved by a single
>  The return value of
>  .BR read (2)
>  is the number of bytes placed in the buffer,
> -or \-1 in case of an error.
> +or \-1 in case of an error (but see BUGS).
>
>  The fields of the
>  .I fanotify_event_metadata
> @@ -468,7 +468,7 @@ The event queue can overflow.
>  In this case, events are lost.
>  .SH BUGS
>  As of Linux 3.15,
> -the following bug exists:
> +the following bugs exists:
>  .IP * 3
>  .\" FIXME: A patch was proposed.
>  When an event is generated,
> @@ -478,6 +478,16 @@ before passing a file descriptor for that file.
>  This poses a security risk, when the
>  .B CAP_SYS_ADMIN
>  capability is set for programs executed by unprivileged users.
> +.IP *
> +If a call to
> +.BR read( 2 )
> +processes multiple events from the fanotify queue and an error occurs, the
> +return value will be the cumulated length of the events successfully copied to
> +the user space buffer before the error occured.
> +The return value will not be \-1.
> +.I errno
> +will not be set.
> +Thus, the user program has no way to detect the error.
>  .SH EXAMPLE
>  The following program demonstrates the usage of the fanotify API.
>  It marks the mount point passed as a command-line argument
> --
> 2.0.0.rc0
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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Re: [PATCH 1/1 v2] fanotify.7: BUGS, error handling in fanotify_read

[Jan Kara]

  Hello,

On Wed 14-05-14 20:52:12, Michael Kerrisk (man-pages) wrote:
> Do you have any comments/additions for this man-pages patch?
  No, it looks good to me. 

								Honza

> On Wed, May 14, 2014 at 8:10 PM, Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org> wrote:
> > The patch in
> > http://www.spinics.net/lists/linux-man/msg05589.html
> > was not accepted.
> >
> > Michael Kerrisk suggested in a private mail to add a comment
> > in the BUGS section.
> >
> > Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
> > ---
> >  man7/fanotify.7 | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/man7/fanotify.7 b/man7/fanotify.7
> > index 2a92908..c6cec7c 100644
> > --- a/man7/fanotify.7
> > +++ b/man7/fanotify.7
> > @@ -164,7 +164,7 @@ so that multiple events can be retrieved by a single
> >  The return value of
> >  .BR read (2)
> >  is the number of bytes placed in the buffer,
> > -or \-1 in case of an error.
> > +or \-1 in case of an error (but see BUGS).
> >
> >  The fields of the
> >  .I fanotify_event_metadata
> > @@ -468,7 +468,7 @@ The event queue can overflow.
> >  In this case, events are lost.
> >  .SH BUGS
> >  As of Linux 3.15,
> > -the following bug exists:
> > +the following bugs exists:
> >  .IP * 3
> >  .\" FIXME: A patch was proposed.
> >  When an event is generated,
> > @@ -478,6 +478,16 @@ before passing a file descriptor for that file.
> >  This poses a security risk, when the
> >  .B CAP_SYS_ADMIN
> >  capability is set for programs executed by unprivileged users.
> > +.IP *
> > +If a call to
> > +.BR read( 2 )
> > +processes multiple events from the fanotify queue and an error occurs, the
> > +return value will be the cumulated length of the events successfully copied to
> > +the user space buffer before the error occured.
> > +The return value will not be \-1.
> > +.I errno
> > +will not be set.
> > +Thus, the user program has no way to detect the error.
> >  .SH EXAMPLE
> >  The following program demonstrates the usage of the fanotify API.
> >  It marks the mount point passed as a command-line argument
> > --
> > 2.0.0.rc0
> >
> 
> 
> 
> -- 
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/
-- 
Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
SUSE Labs, CR
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Re: [PATCH 1/1 v2] fanotify.7: BUGS, error handling in fanotify_read

[Michael Kerrisk (man-pages)]

On 05/14/2014 08:10 PM, Heinrich Schuchardt wrote:
> The patch in
> http://www.spinics.net/lists/linux-man/msg05589.html
> was not accepted.
> 
> Michael Kerrisk suggested in a private mail to add a comment
> in the BUGS section.

Hi Heinrich,

Thanks! I've applied this patch (and fixed a few typos) and added
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>

Cheers,

Michael


> Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
> ---
>  man7/fanotify.7 | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/man7/fanotify.7 b/man7/fanotify.7
> index 2a92908..c6cec7c 100644
> --- a/man7/fanotify.7
> +++ b/man7/fanotify.7
> @@ -164,7 +164,7 @@ so that multiple events can be retrieved by a single
>  The return value of
>  .BR read (2)
>  is the number of bytes placed in the buffer,
> -or \-1 in case of an error.
> +or \-1 in case of an error (but see BUGS).
>  
>  The fields of the
>  .I fanotify_event_metadata
> @@ -468,7 +468,7 @@ The event queue can overflow.
>  In this case, events are lost.
>  .SH BUGS
>  As of Linux 3.15,
> -the following bug exists:
> +the following bugs exists:
>  .IP * 3
>  .\" FIXME: A patch was proposed.
>  When an event is generated,
> @@ -478,6 +478,16 @@ before passing a file descriptor for that file.
>  This poses a security risk, when the
>  .B CAP_SYS_ADMIN
>  capability is set for programs executed by unprivileged users.
> +.IP *
> +If a call to
> +.BR read( 2 )
> +processes multiple events from the fanotify queue and an error occurs, the
> +return value will be the cumulated length of the events successfully copied to
> +the user space buffer before the error occured.
> +The return value will not be \-1.
> +.I errno
> +will not be set.
> +Thus, the user program has no way to detect the error.
>  .SH EXAMPLE
>  The following program demonstrates the usage of the fanotify API.
>  It marks the mount point passed as a command-line argument
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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