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Subject[PATCH v2] staging: lustre: Remove VLA usage
The kernel would like to have all stack VLA usage removed[1]. This switches
to a simple kasprintf() instead, and in the process fixes an off-by-one
between the allocation and the sprintf (allocation did not include NULL
byte in calculation).

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
drivers/staging/lustre/lustre/llite/xattr.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/xattr.c b/drivers/staging/lustre/lustre/llite/xattr.c
index 532384c91447..ff6fe81a4ddb 100644
--- a/drivers/staging/lustre/lustre/llite/xattr.c
+++ b/drivers/staging/lustre/lustre/llite/xattr.c
@@ -87,10 +87,10 @@ ll_xattr_set_common(const struct xattr_handler *handler,
const char *name, const void *value, size_t size,
int flags)
{
- char fullname[strlen(handler->prefix) + strlen(name) + 1];
struct ll_sb_info *sbi = ll_i2sbi(inode);
struct ptlrpc_request *req = NULL;
const char *pv = value;
+ char *fullname;
__u64 valid;
int rc;

@@ -141,10 +141,13 @@ ll_xattr_set_common(const struct xattr_handler *handler,
return -EPERM;
}

- sprintf(fullname, "%s%s\n", handler->prefix, name);
+ fullname = kasprintf(GFP_KERNEL, "%s%s\n", handler->prefix, name);
+ if (!fullname)
+ return -ENOMEM;
rc = md_setxattr(sbi->ll_md_exp, ll_inode2fid(inode),
valid, fullname, pv, size, 0, flags,
ll_i2suppgid(inode), &req);
+ kfree(fullname);
if (rc) {
if (rc == -EOPNOTSUPP && handler->flags == XATTR_USER_T) {
LCONSOLE_INFO("Disabling user_xattr feature because it is not supported on the server\n");
@@ -364,11 +367,11 @@ static int ll_xattr_get_common(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size)
{
- char fullname[strlen(handler->prefix) + strlen(name) + 1];
struct ll_sb_info *sbi = ll_i2sbi(inode);
#ifdef CONFIG_FS_POSIX_ACL
struct ll_inode_info *lli = ll_i2info(inode);
#endif
+ char *fullname;
int rc;

CDEBUG(D_VFSTRACE, "VFS Op:inode=" DFID "(%p)\n",
@@ -411,9 +414,13 @@ static int ll_xattr_get_common(const struct xattr_handler *handler,
if (handler->flags == XATTR_ACL_DEFAULT_T && !S_ISDIR(inode->i_mode))
return -ENODATA;
#endif
- sprintf(fullname, "%s%s\n", handler->prefix, name);
- return ll_xattr_list(inode, fullname, handler->flags, buffer, size,
- OBD_MD_FLXATTR);
+ fullname = kasprintf(GFP_KERNEL, "%s%s\n", handler->prefix, name);
+ if (!fullname)
+ return -ENOMEM;
+ rc = ll_xattr_list(inode, fullname, handler->flags, buffer, size,
+ OBD_MD_FLXATTR);
+ kfree(fullname);
+ return rc;
}

static ssize_t ll_getxattr_lov(struct inode *inode, void *buf, size_t buf_size)
--
2.7.4

--
Kees Cook
Pixel Security

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