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library: eliminated a final potential NULL, <PIDS> api

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In that reference below a specific systemd problem was
fixed in the commit shown. However lurking deep within
the <pids> interface was yet one final case where NULL
could be returned, involving 'strv' and the following:

. a user requested both a single string vector (always
returned as a normal string) & the vectorized version,
as with PROCPS_PIDS_CMDLINE and PROCPS_PIDS_CMDLINE_V.

. a user simply duplicated some vectorized enum items.

The root of that NULL problem is the fact those single
string vectors shared the same proc_t field with their
true vectorized version. So while multiple occurrences
for most strings could be satisfied with strdup versus
the normal ownership usurpation, those true vectorized
fields could not be quite so easily copied/duplicated.

Thus newlib chose to return a NULL result.strv pointer
under either of the above scenarios (which perhaps was
just a user boo-boo in the first place). In any event,
the NULL was a potential for true string vectors only.

Now, since newlib is the sole caller into the readproc
module, separate fields have been created for what are
just normal strings (never vectorized) and those which
remain the true vectorized versions. And, former flags
which only worked if combined, now act as stand alone.

Thus, both PROCPS_PIDS_CMDLINE & PROCPS_PIDS_CMDLINE_V
can be used simultaneously (as they should have been).

Also with this patch, items which a user duplicates in
the stack (beyond the first such item) will return the
the string "[ duplicate ENUM_ID ]". This practice will
apply to both single strings and true vectorized ones.
In addition to informing users of their error, it will
also mean potential NULLs need now never be a concern.

Reference(s);
http://www.freelists.org/post/procps/systemd-binary-vs-library
commit 0580a7b4c6

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2016-05-19 00:00:00 -05:00
committed by Craig Small
parent 8d7945fd0c
commit 09503dc597
3 changed files with 264 additions and 279 deletions
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27
proc/readproc.h
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@ -124,11 +124,15 @@ typedef struct proc_t {
cmin_flt, // stat cumulative min_flt of process and child processes
cmaj_flt; // stat cumulative maj_flt of process and child processes
char
**environ, // (special) environment string vector (/proc/#/environ)
**cmdline, // (special) command line string vector (/proc/#/cmdline)
**cgroup, // (special) cgroup string vector (/proc/#/cgroup)
*supgid, // status supplementary gids as comma delimited str
*supgrp; // supp grp names as comma delimited str, derived from supgid
*environ, // (special) environment as string (/proc/#/environ)
*cmdline, // (special) command line as string (/proc/#/cmdline)
*cgroup, // (special) cgroup as string (/proc/#/cgroup)
*cgname, // (special) name portion of above (if possible)
*supgid, // status supplementary gids as comma delimited str
*supgrp, // supp grp names as comma delimited str, derived from supgid
**environ_v, // (special) environment string vectors (/proc/#/environ)
**cmdline_v, // (special) command line string vectors (/proc/#/cmdline)
**cgroup_v; // (special) cgroup string vectors (/proc/#/cgroup)
char
*euser, // stat(),status effective user name
*ruser, // status real user name
@ -213,14 +217,13 @@ typedef struct PROCTAB {
// id's since uid_t supports no convenient termination sentinel.)
#define PROC_FILLMEM 0x0001 // read statm
#define PROC_FILLCOM 0x0002 // alloc and fill in `cmdline'
#define PROC_FILLENV 0x0004 // alloc and fill in `environ'
#define PROC_FILLARG 0x0002 // alloc and fill in `cmdline' vectors
#define PROC_FILLENV 0x0004 // alloc and fill in `environ' vectors
#define PROC_FILLUSR 0x0008 // resolve user id number -> user name
#define PROC_FILLGRP 0x0010 // resolve group id number -> group name
#define PROC_FILLSTATUS 0x0020 // read status
#define PROC_FILLSTAT 0x0040 // read stat
#define PROC_FILLARG 0x0100 // alloc and fill in `cmdline'
#define PROC_FILLCGROUP 0x0200 // alloc and fill in `cgroup`
#define PROC_FILLCGROUP 0x0200 // alloc and fill in `cgroup` vectors
#define PROC_FILLSUPGRP 0x0400 // resolve supplementary group id -> group name
#define PROC_FILLOOM 0x0800 // fill in proc_t oom_score and oom_adj
#define PROC_FILLNS 0x8000 // fill in proc_t namespace information
@ -233,9 +236,9 @@ typedef struct PROCTAB {
#define PROC_PID 0x1000 // process id numbers ( 0 terminated)
#define PROC_UID 0x4000 // user id numbers ( length needed )
#define PROC_EDITCGRPCVT 0x10000 // edit `cgroup' as single vector
#define PROC_EDITCMDLCVT 0x20000 // edit `cmdline' as single vector
#define PROC_EDITENVRCVT 0x40000 // edit `environ' as single vector
#define PROC_EDITCGRPCVT 0x10000 // edit `cgroup' as regular string
#define PROC_EDITCMDLCVT 0x20000 // edit `cmdline' as regular string
#define PROC_EDITENVRCVT 0x40000 // edit `environ' as regular string
// it helps to give app code a few spare bits
#define PROC_SPARE_1 0x01000000