When enhancing do_shmat I forgot to take into account that shm_lock
is a spinlock, and was allocating memory with the lock held.
This patch fixes that by grabbing a reference to the dentry and
mounts of shm_file before we drop the shm_lock and then performing
the memory allocations.
This is also a bit of a general scrub on the error handling.
Everything is now forced through the single return statement
for clarity, and the handling of the return address now uses
fewer casts.
Signed-off-by: Eric W. Biederman <[email protected]>
---
ipc/shm.c | 56 ++++++++++++++++++++++++++++++++------------------------
1 files changed, 32 insertions(+), 24 deletions(-)
diff --git a/ipc/shm.c b/ipc/shm.c
index e0b6544..26b935b 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -815,15 +815,16 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
unsigned long flags;
unsigned long prot;
int acc_mode;
- void *user_addr;
+ unsigned long user_addr;
struct ipc_namespace *ns;
struct shm_file_data *sfd;
+ struct path path;
mode_t f_mode;
- if (shmid < 0) {
- err = -EINVAL;
+ err = -EINVAL;
+ if (shmid < 0)
goto out;
- } else if ((addr = (ulong)shmaddr)) {
+ else if ((addr = (ulong)shmaddr)) {
if (addr & (SHMLBA-1)) {
if (shmflg & SHM_RND)
addr &= ~(SHMLBA-1); /* round down */
@@ -831,12 +832,12 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
#ifndef __ARCH_FORCE_SHMLBA
if (addr & ~PAGE_MASK)
#endif
- return -EINVAL;
+ goto out;
}
flags = MAP_SHARED | MAP_FIXED;
} else {
if ((shmflg & SHM_REMAP))
- return -EINVAL;
+ goto out;
flags = MAP_SHARED;
}
@@ -860,7 +861,6 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
* additional creator id...
*/
ns = current->nsproxy->ipc_ns;
- err = -EINVAL;
shp = shm_lock(ns, shmid);
if(shp == NULL)
goto out;
@@ -877,19 +877,25 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
if (err)
goto out_unlock;
+ path.dentry = dget(shp->shm_file->f_path.dentry);
+ path.mnt = mntget(shp->shm_file->f_path.mnt);
+ shp->shm_nattch++;
+ size = i_size_read(path.dentry->d_inode);
+ shm_unlock(shp);
+
err = -ENOMEM;
sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
if (!sfd)
- goto out_unlock;
+ goto out_put_path;
+ err = -ENOMEM;
file = get_empty_filp();
if (!file)
goto out_free;
file->f_op = &shm_file_operations;
file->private_data = sfd;
- file->f_path.dentry = dget(shp->shm_file->f_path.dentry);
- file->f_path.mnt = mntget(shp->shm_file->f_path.mnt);
+ file->f_path = path;
file->f_mapping = shp->shm_file->f_mapping;
file->f_mode = f_mode;
sfd->id = shp->id;
@@ -897,13 +903,9 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
sfd->file = shp->shm_file;
sfd->vm_ops = NULL;
- size = i_size_read(file->f_path.dentry->d_inode);
- shp->shm_nattch++;
- shm_unlock(shp);
-
down_write(¤t->mm->mmap_sem);
if (addr && !(shmflg & SHM_REMAP)) {
- user_addr = ERR_PTR(-EINVAL);
+ err = -EINVAL;
if (find_vma_intersection(current->mm, addr, addr + size))
goto invalid;
/*
@@ -915,13 +917,17 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
goto invalid;
}
- user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);
-
+ user_addr = do_mmap (file, addr, size, prot, flags, 0);
+ *raddr = user_addr;
+ err = 0;
+ if (IS_ERR_VALUE(user_addr))
+ err = (long)user_addr;
invalid:
up_write(¤t->mm->mmap_sem);
-
+
fput(file);
+out_nattch:
mutex_lock(&shm_ids(ns).mutex);
shp = shm_lock(ns, shmid);
BUG_ON(!shp);
@@ -933,17 +939,19 @@ invalid:
shm_unlock(shp);
mutex_unlock(&shm_ids(ns).mutex);
- *raddr = (unsigned long) user_addr;
- err = 0;
- if (IS_ERR(user_addr))
- err = PTR_ERR(user_addr);
out:
return err;
-out_free:
- kfree(sfd);
+
out_unlock:
shm_unlock(shp);
goto out;
+
+out_free:
+ kfree(sfd);
+out_put_path:
+ dput(path.dentry);
+ mntput(path.mnt);
+ goto out_nattch;
}
--
1.4.4.1.g278f
-
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