meetakshisetiyaoss@xxxxxxxxx writes:
> From: Shyam Prasad N <sprasad@xxxxxxxxxxxxx>
>
> We recently introduced a password2 field in both ses and ctx structs.
> This was done so as to allow the client to rotate passwords for a mount
> without any downtime. However, when the client transparently handles
> password rotation, it can swap the values of the two password fields
> in the ses struct, but not in smb3_fs_context struct that hangs off
> cifs_sb. This can lead to a situation where a remount unintentionally
> overwrites a working password in the ses struct.
I don't see password rotation being handled for SMB1. I mounted a share
with 'vers=1.0,password=foo,password2=bar' and didn't get any warnings
or errors about it being usupported. I think users would like to have
that.
What about SMB sessions from cifs_tcon::dfs_ses_list? I don't see their
password getting updated over remount.
If you don't plan to support any of the above, then don't allow users to
mount/remount when password rotation can't be handled.
> In order to fix this, we first get the passwords in ctx struct
> in-sync with ses struct, before replacing them with what the passwords
> that could be passed as a part of remount.
>
> Also, in order to avoid race condition between smb2_reconnect and
> smb3_reconfigure, we make sure to lock session_mutex before changing
> password and password2 fields of the ses structure.
>
> Fixes: 35f834265e0d ("smb3: fix broken reconnect when password changing on the server by allowing password rotation")
> Signed-off-by: Shyam Prasad N <sprasad@xxxxxxxxxxxxx>
> Signed-off-by: Meetakshi Setiya <msetiya@xxxxxxxxxxxxx>
> ---
> fs/smb/client/fs_context.c | 69 +++++++++++++++++++++++++++++++++-----
> 1 file changed, 60 insertions(+), 9 deletions(-)
>
> diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
> index 5c5a52019efa..73610e66c8d9 100644
> --- a/fs/smb/client/fs_context.c
> +++ b/fs/smb/client/fs_context.c
> @@ -896,6 +896,7 @@ static int smb3_reconfigure(struct fs_context *fc)
> struct dentry *root = fc->root;
> struct cifs_sb_info *cifs_sb = CIFS_SB(root->d_sb);
> struct cifs_ses *ses = cifs_sb_master_tcon(cifs_sb)->ses;
> + char *new_password = NULL, *new_password2 = NULL;
> bool need_recon = false;
> int rc;
>
> @@ -915,21 +916,71 @@ static int smb3_reconfigure(struct fs_context *fc)
> STEAL_STRING(cifs_sb, ctx, UNC);
> STEAL_STRING(cifs_sb, ctx, source);
> STEAL_STRING(cifs_sb, ctx, username);
> +
> if (need_recon == false)
> STEAL_STRING_SENSITIVE(cifs_sb, ctx, password);
> else {
> - kfree_sensitive(ses->password);
> - ses->password = kstrdup(ctx->password, GFP_KERNEL);
> - if (!ses->password)
> - return -ENOMEM;
> - kfree_sensitive(ses->password2);
> - ses->password2 = kstrdup(ctx->password2, GFP_KERNEL);
> - if (!ses->password2) {
> - kfree_sensitive(ses->password);
> - ses->password = NULL;
> + if (ctx->password) {
> + new_password = kstrdup(ctx->password, GFP_KERNEL);
> + if (!new_password)
> + return -ENOMEM;
> + } else
> + STEAL_STRING_SENSITIVE(cifs_sb, ctx, password);
> + }
> +
> + /*
> + * if a new password2 has been specified, then reset it's value
> + * inside the ses struct
> + */
> + if (ctx->password2) {
> + new_password2 = kstrdup(ctx->password2, GFP_KERNEL);
> + if (!new_password2) {
> + if (new_password)
Useless non-NULL check as kfree_sensitive() already handles it.
> + kfree_sensitive(new_password);
> return -ENOMEM;
> }
> + } else
> + STEAL_STRING_SENSITIVE(cifs_sb, ctx, password2);
> +
> + /*
> + * we may update the passwords in the ses struct below. Make sure we do
> + * not race with smb2_reconnect
> + */
> + mutex_lock(&ses->session_mutex);
> +
> + /*
> + * smb2_reconnect may swap password and password2 in case session setup
> + * failed. First get ctx passwords in sync with ses passwords. It should
> + * be okay to do this even if this function were to return an error at a
> + * later stage
> + */
> + if (ses->password &&
> + cifs_sb->ctx->password &&
> + strcmp(ses->password, cifs_sb->ctx->password)) {
> + kfree_sensitive(cifs_sb->ctx->password);
> + cifs_sb->ctx->password = kstrdup(ses->password, GFP_KERNEL);
Missing allocation failure check.
> + }
> + if (ses->password2 &&
> + cifs_sb->ctx->password2 &&
> + strcmp(ses->password2, cifs_sb->ctx->password2)) {
> + kfree_sensitive(cifs_sb->ctx->password2);
> + cifs_sb->ctx->password2 = kstrdup(ses->password2, GFP_KERNEL);
Ditto.
> + }
> +
> + /*
> + * now that allocations for passwords are done, commit them
> + */
> + if (new_password) {
> + kfree_sensitive(ses->password);
> + ses->password = new_password;
> + }
> + if (new_password2) {
> + kfree_sensitive(ses->password2);
> + ses->password2 = new_password2;
> }
> +
> + mutex_unlock(&ses->session_mutex);
> +
> STEAL_STRING(cifs_sb, ctx, domainname);
> STEAL_STRING(cifs_sb, ctx, nodename);
> STEAL_STRING(cifs_sb, ctx, iocharset);
> --
> 2.46.0.46.g406f326d27
