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ltp: Fix races in mmap1

PATCH In review Dave Kleikamp 3 participants 3 messages Aug 28, 2013

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Dave Kleikamp

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#0 lore raw

PATCH 1/1 ltp: Fix races in mmap1

Make map_address a volatile pointer so that it is dereferenced in read_mem() after read_lock is set.

Also read_lock must protect the verbose printf that reads from map_address as well.

Signed-off-by Dave Kleikamp <[email protected]>
testcases/kernel/mem/mtest06/mmap1.c +5 -3
index 7c80bb4..cd1127f 100644
@@ -62,7 +62,7 @@
 } while (0)
 
 static int verbose_print = 0;
-static char *map_address;
+static char *volatile map_address;
 static jmp_buf jmpbuf;
 static volatile char read_lock = 0;
 

@@ -228,11 +228,13 @@ void *read_mem(void *ptr)
 				tst_resm(TINFO, "page fault occurred due to "
 					 "a read after an unmap");
 		} else {
-			if (verbose_print)
+			if (verbose_print) {
+				read_lock = 1;
 				tst_resm(TINFO,
 					 "read_mem(): content of memory: %s",
 					 (char *)map_address);
-
+				read_lock = 0;
+			}
 			for (j = 0; j < args[1]; j++) {
 				read_lock = 1;
 				if (map_address[j] != 'a')

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#1 lore raw
Quoted 40 lines · Dave Kleikamp

Make map_address a volatile pointer so that it is dereferenced in read_mem() after read_lock is set.

Also read_lock must protect the verbose printf that reads from map_address as well.

Signed-off-by Dave Kleikamp <[email protected]>
testcases/kernel/mem/mtest06/mmap1.c +5 -4
index 7c80bb4..cd1127f 100644
@@ -62,7 +62,7 @@
  } while (0)
 
  static int verbose_print = 0;
-static char *map_address;
+static char *volatile map_address;
  static jmp_buf jmpbuf;
  static volatile char read_lock = 0;
 

@@ -228,11 +228,13 @@ void *read_mem(void *ptr)
  				tst_resm(TINFO, "page fault occurred due to "
  					 "a read after an unmap");
  		} else {
-			if (verbose_print)
+			if (verbose_print) {
+				read_lock = 1;
  				tst_resm(TINFO,
  					 "read_mem(): content of memory: %s",
  					 (char *)map_address);
-
+				read_lock = 0;
+			}
  			for (j = 0; j < args[1]; j++) {
  				read_lock = 1;
  				if (map_address[j] != 'a')
 
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Quoted 8 lines

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Just in case.. To reproduce failures we need to invoke the test this way, for example:

./mmap1 -v -s 10

and then wait few minutes (it depends...)

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#2 lore raw
In reply to Dave Kleikamp

Hi!

testcases/kernel/mem/mtest06/mmap1.c line 65

Quoted 3 lines

static int verbose_print = 0;

testcases/kernel/mem/mtest06/mmap1.c +1 -1
-static char *map_address;
+static char *volatile map_address;

Ok.

Quoted 9 lines

static jmp_buf jmpbuf;
static volatile char read_lock = 0;

testcases/kernel/mem/mtest06/mmap1.c +1 -1
@@ -228,11 +228,13 @@ void *read_mem(void *ptr)
 				tst_resm(TINFO, "page fault occurred due to "
 					 "a read after an unmap");
 		} else {
-			if (verbose_print)
+			if (verbose_print) {

testcases/kernel/mem/mtest06/mmap1.c void *read_mem(void *ptr) · line 240

Quoted 10 lines
testcases/kernel/mem/mtest06/mmap1.c +3 -1
+				read_lock = 1;
 				tst_resm(TINFO,
 					 "read_mem(): content of memory: %s",
 					 (char *)map_address);
-
+				read_lock = 0;
+			}
 			for (j = 0; j < args[1]; j++) {
 				read_lock = 1;
 				if (map_address[j] != 'a')

Good catch, I've overlooked the tst_resm() when I was fixing the testcase.

Commited, thanks.

Signature · 13 lines
Cyril Hrubis
[email protected]

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and advance your career. Get an incredible 1,500+ hours of step-by-step
tutorial videos with LearnDevNow. Subscribe today and save!
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