[PATCH 04/29] xfs: use strndup_user in XFS_IOC_ATTRMULTI_BY_HANDLE

Christoph Hellwig
2020-01-14T08:15:29Z

Simplify the user copy code by using strndup_user. This means that we
now do one memory allocation per operation instead of one per ioctl,
but memory allocations are cheap compared to the actual file system
operations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/xfs_ioctl.c | 17 +++++------------
fs/xfs/xfs_ioctl32.c | 17 +++++------------
2 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 6bd0684a3528..f4d5c865e29e 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -446,11 +446,6 @@ xfs_attrmulti_by_handle(
goto out_dput;
}

- error = -ENOMEM;
- attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
- if (!attr_name)
- goto out_kfree_ops;
-
error = 0;
for (i = 0; i < am_hreq.opcount; i++) {
if ((ops[i].am_flags & ATTR_ROOT) &&
@@ -460,12 +455,11 @@ xfs_attrmulti_by_handle(
}
ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;

- ops[i].am_error = strncpy_from_user((char *)attr_name,
- ops[i].am_attrname, MAXNAMELEN);
- if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
- error = -ERANGE;
- if (ops[i].am_error < 0)
+ attr_name = strndup_user(ops[i].am_attrname, MAXNAMELEN);
+ if (IS_ERR(attr_name)) {
+ ops[i].am_error = PTR_ERR(attr_name);
break;
+ }

switch (ops[i].am_opcode) {
case ATTR_OP_GET:
@@ -496,13 +490,12 @@ xfs_attrmulti_by_handle(
default:
ops[i].am_error = -EINVAL;
}
+ kfree(attr_name);
}

if (copy_to_user(am_hreq.ops, ops, size))
error = -EFAULT;

- kfree(attr_name);
- out_kfree_ops:
kfree(ops);
out_dput:
dput(dentry);
diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
index 1092c66e48d6..e6a7f619a54c 100644
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -443,11 +443,6 @@ xfs_compat_attrmulti_by_handle(
goto out_dput;
}

- error = -ENOMEM;
- attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
- if (!attr_name)
- goto out_kfree_ops;
-
error = 0;
for (i = 0; i < am_hreq.opcount; i++) {
if ((ops[i].am_flags & ATTR_ROOT) &&
@@ -457,13 +452,12 @@ xfs_compat_attrmulti_by_handle(
}
ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;

- ops[i].am_error = strncpy_from_user((char *)attr_name,
- compat_ptr(ops[i].am_attrname),
+ attr_name = strndup_user(compat_ptr(ops[i].am_attrname),
MAXNAMELEN);
- if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
- error = -ERANGE;
- if (ops[i].am_error < 0)
+ if (IS_ERR(attr_name)) {
+ ops[i].am_error = PTR_ERR(attr_name);
break;
+ }

switch (ops[i].am_opcode) {
case ATTR_OP_GET:
@@ -494,13 +488,12 @@ xfs_compat_attrmulti_by_handle(
default:
ops[i].am_error = -EINVAL;
}
+ kfree(attr_name);
}

if (copy_to_user(compat_ptr(am_hreq.ops), ops, size))
error = -EFAULT;

- kfree(attr_name);
- out_kfree_ops:
kfree(ops);
out_dput:
dput(dentry);
--
2.24.1