minor tail.c changes

[Jim Meyering]

I'm not certain that the buffer overrun in 1/3 can actually
be triggered, but it's worth repairing before anything else.

Also, I found the internal name, wd_table, to be inadequate,
so now it's called wd_to_name.


>From 66b15949df877a75a413ad40e88aa89c3c467d34 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 29 Dec 2009 14:24:01 +0100
Subject: [PATCH 1/3] tail: avoid read-beyond-end-of-buffer error

* src/tail.c (tail_forever_inotify): Do not use f[i] in a context
where i may be larger than the largest valid index.  In the final
"if" clause in which we'd remove an inotify watch, we might have
used f[n_files].  Use fspec instead, since it is guaranteed to
be defined.
---
 src/tail.c |   27 +++++++++++++--------------
 1 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/src/tail.c b/src/tail.c
index 89f37f6..2bbf5c4 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1264,7 +1264,6 @@ wd_comparator (const void *e1, const void *e2)
 }

 /* Helper function used by `tail_forever_inotify'.  */
-
 static void
 check_fspec (struct File_spec *fspec, int wd, int *prev_wd)
 {
@@ -1306,12 +1305,10 @@ check_fspec (struct File_spec *fspec, int wd, int 
*prev_wd)

 /* Tail N_FILES files forever, or until killed.
    Check modifications using the inotify events system.  */
-
 static void
 tail_forever_inotify (int wd, struct File_spec *f, size_t n_files,
                       double sleep_interval)
 {
-  size_t i;
   unsigned int max_realloc = 3;
   Hash_table *wd_table;

@@ -1330,6 +1327,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
   /* Add an inotify watch for each watched file.  If -F is specified then watch
      its parent directory too, in this way when they re-appear we can add them
      again to the watch list.  */
+  size_t i;
   for (i = 0; i < n_files; i++)
     {
       if (!f[i].ignore)
@@ -1459,34 +1457,35 @@ tail_forever_inotify (int wd, struct File_spec *f, 
size_t n_files,

       if (ev->len) /* event on ev->name in watched directory  */
         {
-          for (i = 0; i < n_files; i++)
+          size_t j;
+          for (j = 0; j < n_files; j++)
             {
               /* With N=hundreds of frequently-changing files, this O(N^2)
                  process might be a problem.  FIXME: use a hash table?  */
-              if (f[i].parent_wd == ev->wd
-                  && STREQ (ev->name, f[i].name + f[i].basename_start))
+              if (f[j].parent_wd == ev->wd
+                  && STREQ (ev->name, f[j].name + f[j].basename_start))
                 break;
             }

           /* It is not a watched file.  */
-          if (i == n_files)
+          if (j == n_files)
             continue;

           /* It's fine to add the same file more than once.  */
-          f[i].wd = inotify_add_watch (wd, f[i].name, inotify_wd_mask);
+          f[j].wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask);

-          if (f[i].wd < 0)
+          if (f[j].wd < 0)
             {
-              error (0, errno, _("cannot watch %s"), quote (f[i].name));
+              error (0, errno, _("cannot watch %s"), quote (f[j].name));
               continue;
             }

-          fspec = &(f[i]);
+          fspec = &(f[j]);
           if (hash_insert (wd_table, fspec) == NULL)
             xalloc_die ();

           if (follow_mode == Follow_name)
-            recheck (&(f[i]), false);
+            recheck (&(f[j]), false);
         }
       else
         {
@@ -1508,8 +1507,8 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
           if ((ev->mask & IN_DELETE_SELF)
               || ((ev->mask & IN_MOVE_SELF) && follow_mode == 
Follow_descriptor))
             {
-              inotify_rm_watch (wd, f[i].wd);
-              hash_delete (wd_table, &(f[i]));
+              inotify_rm_watch (wd, fspec->wd);
+              hash_delete (wd_table, fspec);
             }
           if (follow_mode == Follow_name)
             recheck (fspec, false);
--
1.6.6.301.g5794


>From 4b2b2711d9f12b991d29755810e090133510f0d2 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 29 Dec 2009 14:26:05 +0100
Subject: [PATCH 2/3] tail: rename an internal variable

* src/tail.c (tail_forever_inotify): s/wd_table/wd_to_name/
---
 src/tail.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/tail.c b/src/tail.c
index 2bbf5c4..8e6c8ac 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1310,7 +1310,9 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
                       double sleep_interval)
 {
   unsigned int max_realloc = 3;
-  Hash_table *wd_table;
+
+  /* Map an inotify watch descriptor to the name of the file it's watching.  */
+  Hash_table *wd_to_name;

   bool found_watchable = false;
   bool writer_is_dead = false;
@@ -1320,8 +1322,8 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
   size_t evbuf_off = 0;
   size_t len = 0;

-  wd_table = hash_initialize (n_files, NULL, wd_hasher, wd_comparator, NULL);
-  if (! wd_table)
+  wd_to_name = hash_initialize (n_files, NULL, wd_hasher, wd_comparator, NULL);
+  if (! wd_to_name)
     xalloc_die ();

   /* Add an inotify watch for each watched file.  If -F is specified then watch
@@ -1371,7 +1373,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
               continue;
             }

-          if (hash_insert (wd_table, &(f[i])) == NULL)
+          if (hash_insert (wd_to_name, &(f[i])) == NULL)
             xalloc_die ();

           found_watchable = true;
@@ -1481,7 +1483,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
             }

           fspec = &(f[j]);
-          if (hash_insert (wd_table, fspec) == NULL)
+          if (hash_insert (wd_to_name, fspec) == NULL)
             xalloc_die ();

           if (follow_mode == Follow_name)
@@ -1491,7 +1493,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
         {
           struct File_spec key;
           key.wd = ev->wd;
-          fspec = hash_lookup (wd_table, &key);
+          fspec = hash_lookup (wd_to_name, &key);
         }

       if (! fspec)
@@ -1508,7 +1510,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t 
n_files,
               || ((ev->mask & IN_MOVE_SELF) && follow_mode == 
Follow_descriptor))
             {
               inotify_rm_watch (wd, fspec->wd);
-              hash_delete (wd_table, fspec);
+              hash_delete (wd_to_name, fspec);
             }
           if (follow_mode == Follow_name)
             recheck (fspec, false);
--
1.6.6.301.g5794


>From ed86ca7c5e4e67b59ce5cb592fef075765c7893a Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 29 Dec 2009 14:31:56 +0100
Subject: [PATCH 3/3] maint: quiet "make" in doc/

* doc/Makefile.am (constants.texi): Add a use of AM_V_GEN.
---
 doc/Makefile.am |   13 ++++++-------
 1 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/doc/Makefile.am b/doc/Makefile.am
index 224bcd8..c151333 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -30,13 +30,12 @@ EXTRA_DIST = perm.texi getdate.texi constants.texi fdl.texi
 AM_MAKEINFOFLAGS = --no-split

 constants.texi: $(top_srcdir)/src/tail.c $(top_srcdir)/src/shred.c
-       LC_ALL=C \
-       sed -n -e 's/^#define \(DEFAULT_MAX[_A-Z]*\) \(.*\)/@set \1 \2/p' \
-         $(top_srcdir)/src/tail.c > t-$@
-       LC_ALL=C \
-       sed -n -e 's/.*\(DEFAULT_PASSES\)[ =]* \([0-9]*\).*/@set SHRED_\1 \2/p'\
-         $(top_srcdir)/src/shred.c >> t-$@
-       mv t-$@ $@
+       $(AM_V_GEN)LC_ALL=C; export LC_ALL; \
+       { sed -n -e 's/^#define \(DEFAULT_MAX[_A-Z]*\) \(.*\)/@set \1 \2/p' \
+           $(top_srcdir)/src/tail.c && \
+         sed -n -e 's/.*\(DEFAULT_PASSES\)[ =]* \([0-9]*\).*/@set SHRED_\1 
\2/p'\
+           $(top_srcdir)/src/shred.c; } > t-$@ \
+         && mv t-$@ $@

 MAINTAINERCLEANFILES = constants.texi

--
1.6.6.301.g5794