[PATCH] proc.5: Clarify the format of /proc/$PID/cmdline

[PATCH] proc.5: Clarify the format of /proc/$PID/cmdline

[Günther Noack]

It is possible to produce /proc/$PID/cmdline files which do not follow
the NUL-seperated format, by using the tricks described in the
paragraph below.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 man5/proc.5 | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/man5/proc.5 b/man5/proc.5
index a9bb175e8..a16479634 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -497,10 +497,21 @@ unless the process is a zombie.
 .\" In Linux 2.3.26, this also used to be true if the process was swapped out.
 In the latter case, there is nothing in this file:
 that is, a read on this file will return 0 characters.
-The command-line arguments appear in this file as a set of
-strings separated by null bytes (\[aq]\e0\[aq]),
+.IP
+For processes which are still running,
+the command-line arguments appear in this file
+in the same layout as they do in process memory:
+If the process is well-behaved,
+it is a set of strings separated by null bytes (\[aq]\e0\[aq]),
 with a further null byte after the last string.
 .IP
+This is the common case,
+but processes have the freedom to override
+the memory region and break assumptions
+about the contents or format of the
+.IR /proc/ pid /cmdline
+file.
+.IP
 If, after an
 .BR execve (2),
 the process modifies its

base-commit: 4ca216bacc7d185c1af3c384ab53cd1ec74830d1
-- 
2.40.1.698.g37aff9b760-goog

Re: [PATCH] proc.5: Clarify the format of /proc/$PID/cmdline

[Alejandro Colomar]

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Hi Günther!

On 5/24/23 16:33, Günther Noack wrote:
> It is possible to produce /proc/$PID/cmdline files which do not follow
> the NUL-seperated format, by using the tricks described in the
> paragraph below.
> 
> Signed-off-by: Günther Noack <gnoack@google.com>

Thanks!  Patch applied.

Cheers,
Alex

> ---
>  man5/proc.5 | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/man5/proc.5 b/man5/proc.5
> index a9bb175e8..a16479634 100644
> --- a/man5/proc.5
> +++ b/man5/proc.5
> @@ -497,10 +497,21 @@ unless the process is a zombie.
>  .\" In Linux 2.3.26, this also used to be true if the process was swapped out.
>  In the latter case, there is nothing in this file:
>  that is, a read on this file will return 0 characters.
> -The command-line arguments appear in this file as a set of
> -strings separated by null bytes (\[aq]\e0\[aq]),
> +.IP
> +For processes which are still running,
> +the command-line arguments appear in this file
> +in the same layout as they do in process memory:
> +If the process is well-behaved,
> +it is a set of strings separated by null bytes (\[aq]\e0\[aq]),
>  with a further null byte after the last string.
>  .IP
> +This is the common case,
> +but processes have the freedom to override
> +the memory region and break assumptions
> +about the contents or format of the
> +.IR /proc/ pid /cmdline
> +file.
> +.IP
>  If, after an
>  .BR execve (2),
>  the process modifies its
> 
> base-commit: 4ca216bacc7d185c1af3c384ab53cd1ec74830d1

-- 
<http://www.alejandro-colomar.es/>
GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5

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