[PATCH] histfile: fix mmap page alignment

[Grisha Levit]

The mmap in history_do_write would usually fail when appending because
the offset must be a multiple of the page size.
---
 lib/readline/histfile.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/readline/histfile.c b/lib/readline/histfile.c
index a5fb11d2..d5568152 100644
--- a/lib/readline/histfile.c
+++ b/lib/readline/histfile.c
@@ -742,7 +742,7 @@ history_do_write (const char *filename, int nelements, int 
overwrite)
   int file, mode, rv, exists;
   struct stat finfo;
 #ifdef HISTORY_USE_MMAP
-  size_t cursize;
+  size_t cursize, pa_size;
 
   history_lines_written_to_file = 0;
 
@@ -798,7 +798,10 @@ history_do_write (const char *filename, int nelements, int 
overwrite)
 #ifdef HISTORY_USE_MMAP
     if (ftruncate (file, buffer_size+cursize) == -1)
       goto mmap_error;
-    buffer = (char *)mmap (0, buffer_size, PROT_READ|PROT_WRITE, MAP_WFLAGS, 
file, cursize);
+
+    /* offset for mmap() must be page aligned */
+    pa_size = cursize & ~(getpagesize() - 1);
+    buffer = (char *)mmap (0, buffer_size + cursize - pa_size, 
PROT_READ|PROT_WRITE, MAP_WFLAGS, file, pa_size);
     if ((void *)buffer == MAP_FAILED)
       {
 mmap_error:
@@ -812,6 +815,7 @@ mmap_error:
        FREE (tempname);
        return rv;
       }
+    j = cursize - pa_size;
 #else    
     buffer = (char *)malloc (buffer_size);
     if (buffer == 0)
@@ -826,9 +830,10 @@ mmap_error:
        FREE (tempname);
        return rv;
       }
+    j = 0;
 #endif
 
-    for (j = 0, i = history_length - nelements; i < history_length; i++)
+    for (i = history_length - nelements; i < history_length; i++)
       {
        if (history_write_timestamps && the_history[i]->timestamp && 
the_history[i]->timestamp[0])
          {
@@ -842,7 +847,9 @@ mmap_error:
       }
 
 #ifdef HISTORY_USE_MMAP
-    if (msync (buffer, buffer_size, MS_ASYNC) != 0 || munmap (buffer, 
buffer_size) != 0)
+    if (msync (buffer, buffer_size + cursize - pa_size, MS_ASYNC) != 0)
+      rv = errno;
+    if (munmap (buffer, buffer_size + cursize - pa_size) != 0 && rv == 0)
       rv = errno;
 #else
     if (write (file, buffer, buffer_size) < 0)
-- 
2.47.0