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authorAl Viro <viro@zeniv.linux.org.uk>2009-03-30 07:20:30 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2009-03-31 23:00:26 -0400
commit498052bba55ecaff58db6a1436b0e25bfd75a7ff (patch)
treebd3644ac60737e3733995a203acebd70cfd1b21b /fs/compat.c
parent3e93cd671813e204c258f1e6c797959920cf7772 (diff)
downloadlwn-498052bba55ecaff58db6a1436b0e25bfd75a7ff.tar.gz
lwn-498052bba55ecaff58db6a1436b0e25bfd75a7ff.zip
New locking/refcounting for fs_struct
* all changes of current->fs are done under task_lock and write_lock of old fs->lock * refcount is not atomic anymore (same protection) * its decrements are done when removing reference from current; at the same time we decide whether to free it. * put_fs_struct() is gone * new field - ->in_exec. Set by check_unsafe_exec() if we are trying to do execve() and only subthreads share fs_struct. Cleared when finishing exec (success and failure alike). Makes CLONE_FS fail with -EAGAIN if set. * check_unsafe_exec() may fail with -EAGAIN if another execve() from subthread is in progress. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/compat.c')
-rw-r--r--fs/compat.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/fs/compat.c b/fs/compat.c
index 55efdfebdf5a..baabf203b847 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -51,6 +51,7 @@
#include <linux/poll.h>
#include <linux/mm.h>
#include <linux/eventpoll.h>
+#include <linux/fs_struct.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
@@ -1441,12 +1442,15 @@ int compat_do_execve(char * filename,
bprm->cred = prepare_exec_creds();
if (!bprm->cred)
goto out_unlock;
- check_unsafe_exec(bprm);
+
+ retval = check_unsafe_exec(bprm);
+ if (retval)
+ goto out_unlock;
file = open_exec(filename);
retval = PTR_ERR(file);
if (IS_ERR(file))
- goto out_unlock;
+ goto out_unmark;
sched_exec();
@@ -1488,6 +1492,9 @@ int compat_do_execve(char * filename,
goto out;
/* execve succeeded */
+ write_lock(&current->fs->lock);
+ current->fs->in_exec = 0;
+ write_unlock(&current->fs->lock);
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
acct_update_integrals(current);
@@ -1506,6 +1513,11 @@ out_file:
fput(bprm->file);
}
+out_unmark:
+ write_lock(&current->fs->lock);
+ current->fs->in_exec = 0;
+ write_unlock(&current->fs->lock);
+
out_unlock:
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);