On 1/5/22 5:22 AM, Christian Brauner wrote:
> On Tue, Jan 04, 2022 at 11:09:34AM -0800, Stefan Roesch wrote:
>> This splits off do_getxattr function from the getxattr
>> function. This will allow io_uring to call it from its
>> io worker.
>>
>> Signed-off-by: Stefan Roesch <shr@xxxxxx>
>> Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
>> ---
>> fs/internal.h | 7 +++++++
>> fs/xattr.c | 32 ++++++++++++++++++++------------
>> 2 files changed, 27 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/internal.h b/fs/internal.h
>> index 00c98b0cd634..942b2005a2be 100644
>> --- a/fs/internal.h
>> +++ b/fs/internal.h
>> @@ -220,6 +220,13 @@ struct xattr_ctx {
>> unsigned int flags;
>> };
>>
>> +
>> +ssize_t do_getxattr(struct user_namespace *mnt_userns,
>> + struct dentry *d,
>> + const char *kname,
>> + void __user *value,
>> + size_t size);
>> +
>> int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
>> int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>> struct xattr_ctx *ctx);
>> diff --git a/fs/xattr.c b/fs/xattr.c
>> index dec7ac3e0e89..7f2b805ed56c 100644
>> --- a/fs/xattr.c
>> +++ b/fs/xattr.c
>> @@ -675,19 +675,12 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
>> /*
>> * Extended attribute GET operations
>> */
>> -static ssize_t
>> -getxattr(struct user_namespace *mnt_userns, struct dentry *d,
>> - const char __user *name, void __user *value, size_t size)
>> +ssize_t
>> +do_getxattr(struct user_namespace *mnt_userns, struct dentry *d,
>> + const char *kname, void __user *value, size_t size)
>> {
>> - ssize_t error;
>> void *kvalue = NULL;
>> - char kname[XATTR_NAME_MAX + 1];
>> -
>> - error = strncpy_from_user(kname, name, sizeof(kname));
>> - if (error == 0 || error == sizeof(kname))
>> - error = -ERANGE;
>> - if (error < 0)
>> - return error;
>> + ssize_t error;
>>
>> if (size) {
>> if (size > XATTR_SIZE_MAX)
>> @@ -711,10 +704,25 @@ getxattr(struct user_namespace *mnt_userns, struct dentry *d,
>> }
>>
>> kvfree(kvalue);
>> -
>> return error;
>> }
>>
>> +static ssize_t
>> +getxattr(struct user_namespace *mnt_userns, struct dentry *d,
>> + const char __user *name, void __user *value, size_t size)
>> +{
>> + ssize_t error;
>> + struct xattr_name kname;
>> +
>> + error = strncpy_from_user(kname.name, name, sizeof(kname.name));
>> + if (error == 0 || error == sizeof(kname.name))
>> + error = -ERANGE;
>> + if (error < 0)
>> + return error;
>> +
>> + return do_getxattr(mnt_userns, d, kname.name, value, size);
>> +}
>
> Fwiw, this could have the same signature as do_setxattr(). So sm along
> the lines of (completely untested):
>
Christian, I made changes similar to the ones you recommended.
However I needed to introduce a union in the xattr_ctx structure.
For the setxattr function we require a const pointer and for getxattr
function we only require a pointer.
In addition it also needs changes in io_uring.c to pass in the context.
v12 has these changes.
> Subject: [PATCH] UNTESTED
>
> ---
> fs/internal.h | 8 ++------
> fs/xattr.c | 36 ++++++++++++++++++++++--------------
> 2 files changed, 24 insertions(+), 20 deletions(-)
>
> diff --git a/fs/internal.h b/fs/internal.h
> index 942b2005a2be..d2332496724b 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -220,12 +220,8 @@ struct xattr_ctx {
> unsigned int flags;
> };
>
> -
> -ssize_t do_getxattr(struct user_namespace *mnt_userns,
> - struct dentry *d,
> - const char *kname,
> - void __user *value,
> - size_t size);
> +ssize_t do_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> + struct xattr_ctx *ctx);
>
> int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
> int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 7f2b805ed56c..52bcfe149a9f 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -675,35 +675,34 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
> /*
> * Extended attribute GET operations
> */
> -ssize_t
> -do_getxattr(struct user_namespace *mnt_userns, struct dentry *d,
> - const char *kname, void __user *value, size_t size)
> +ssize_t do_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> + struct xattr_ctx *ctx)
> +
> {
> - void *kvalue = NULL;
> ssize_t error;
> + char *kname = ctx->kname.name;
>
> - if (size) {
> - if (size > XATTR_SIZE_MAX)
> - size = XATTR_SIZE_MAX;
> - kvalue = kvzalloc(size, GFP_KERNEL);
> - if (!kvalue)
> + if (ctx->size) {
> + if (ctx->size > XATTR_SIZE_MAX)
> + ctx->size = XATTR_SIZE_MAX;
> + ctx->kvalue = kvzalloc(ctx->size, GFP_KERNEL);
> + if (!ctx->kvalue)
> return -ENOMEM;
> }
>
> - error = vfs_getxattr(mnt_userns, d, kname, kvalue, size);
> + error = vfs_getxattr(mnt_userns, d, kname, ctx->kvalue, ctx->size);
> if (error > 0) {
> if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
> (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
> posix_acl_fix_xattr_to_user(mnt_userns, kvalue, error);
> - if (size && copy_to_user(value, kvalue, error))
> + if (ctx->size && copy_to_user(value, kvalue, error))
> error = -EFAULT;
> - } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
> + } else if (error == -ERANGE && ctx->size >= XATTR_SIZE_MAX) {
> /* The file system tried to returned a value bigger
> than XATTR_SIZE_MAX bytes. Not possible. */
> error = -E2BIG;
> }
>
> - kvfree(kvalue);
> return error;
> }
>
> @@ -713,6 +712,12 @@ getxattr(struct user_namespace *mnt_userns, struct dentry *d,
> {
> ssize_t error;
> struct xattr_name kname;
> + struct xattr_ctx ctx = {
> + .value = value,
> + .kvalue = NULL,
> + .size = size,
> + .kname = &kname,
> + };
>
> error = strncpy_from_user(kname.name, name, sizeof(kname.name));
> if (error == 0 || error == sizeof(kname.name))
> @@ -720,7 +725,10 @@ getxattr(struct user_namespace *mnt_userns, struct dentry *d,
> if (error < 0)
> return error;
>
> - return do_getxattr(mnt_userns, d, kname.name, value, size);
> + error = do_getxattr(mnt_userns, d, &ctx);
> +
> + kvfree(ctx.kvalue);
> + return error;
> }
>
> static ssize_t path_getxattr(const char __user *pathname,
