RE: futex question

From: Anirban Sinha
Date: Thu Oct 01 2009 - 19:47:02 EST



> Should we not just clear the pointer (and
>> it's compat version) within do_execve()?


In our private repository, applying the following patch resolved the
issues I mentioned. I no longer see messages like this:

[futex] ("ifconfig")(pid=2509) exit_robust_list:unable to fetch robust
entry. uaddr=0x000000002abbc4f0

from my instrumented kernel within exit_robust_list(). My
instrumentation looked something like this:

if (fetch_robust_entry(...)) {
printk(...);
return;
}

Just tossing the patch in the community in case someone is interested
...



Signed-off-by: Anirban Sinha <asinha@xxxxxxxxxxxxxxxxx>
---
fs/compat.c | 3 +++
fs/exec.c | 3 +++
2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/compat.c b/fs/compat.c
index 6d6f98f..c3d117c 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1510,6 +1510,9 @@ int compat_do_execve(char * filename,
if (retval)
goto out_file;

+#ifdef CONFIG_FUTEX
+ current->compat_robust_list = NULL;
+#endif
bprm->argc = compat_count(argv, MAX_ARG_STRINGS);
if ((retval = bprm->argc) < 0)
goto out;
diff --git a/fs/exec.c b/fs/exec.c
index 172ceb6..e9334b8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1323,6 +1323,9 @@ int do_execve(char * filename,
retval = bprm_mm_init(bprm);
if (retval)
goto out_file;
+#ifdef CONFIG_FUTEX
+ current->robust_list = NULL;
+#endif

bprm->argc = count(argv, MAX_ARG_STRINGS);
if ((retval = bprm->argc) < 0)


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