re: NFS: inter ssc open (memory leak detected)

[Colin Ian King]

Hi,

Static analysis with Coverity has detected a memory leak in the
following commit:

commit ec4b0925089826af45e99cdf78a8ac84c1d005f1
Author: Olga Kornievskaia <kolga@xxxxxxxxxx>
Date:   Tue Oct 8 16:33:53 2019 -0400

    NFS: inter ssc open


In function nfs42_ssc_open(), fs/nfs/nfs4file.c, analysis is as follows:

   3. alloc_fn: Storage is returned from allocation function kzalloc.
   4. var_assign: Assigning: read_name = storage returned from
kzalloc(len, 3136U).
336        read_name = kzalloc(len, GFP_NOFS);

   5. Condition read_name == NULL, taking false branch.
337        if (read_name == NULL)
338                goto out;

   6. noescape: Resource read_name is not freed or pointed-to in snprintf.
339        snprintf(read_name, len, SSC_READ_NAME_BODY, read_name_gen++);
340
341        r_ino = nfs_fhget(ss_mnt->mnt_root->d_inode->i_sb, src_fh,
&fattr,
342                        NULL);

   7. Condition IS_ERR(r_ino), taking true branch.
343        if (IS_ERR(r_ino)) {
344                res = ERR_CAST(r_ino);

   8. Jumping to label out.
345                goto out;
346        }
347
348        filep = alloc_file_pseudo(r_ino, ss_mnt, read_name, FMODE_READ,
349                                     r_ino->i_fop);
350        if (IS_ERR(filep)) {
351                res = ERR_CAST(filep);
352                goto out;
353        }
354        filep->f_mode |= FMODE_READ;
355
356        ctx = alloc_nfs_open_context(filep->f_path.dentry, filep->f_mode,
357                                        filep);
358        if (IS_ERR(ctx)) {
359                res = ERR_CAST(ctx);
360                goto out_filep;
361        }
362
363        res = ERR_PTR(-EINVAL);
364        sp = nfs4_get_state_owner(server, ctx->cred, GFP_KERNEL);
365        if (sp == NULL)
366                goto out_ctx;
367
368        ctx->state = nfs4_get_open_state(r_ino, sp);
369        if (ctx->state == NULL)
370                goto out_stateowner;
371
372        set_bit(NFS_SRV_SSC_COPY_STATE, &ctx->state->flags);
373        set_bit(NFS_OPEN_STATE, &ctx->state->flags);
374        memcpy(&ctx->state->open_stateid.other, &stateid->other,
375               NFS4_STATEID_OTHER_SIZE);
376        update_open_stateid(ctx->state, stateid, NULL, filep->f_mode);
377
378        nfs_file_set_open_context(filep, ctx);
379        put_nfs_open_context(ctx);
380
381        file_ra_state_init(&filep->f_ra,
filep->f_mapping->host->i_mapping);
382        res = filep;
383out:

   CID 91575 (#1-2 of 2): Resource leak (RESOURCE_LEAK)

9. leaked_storage: Variable read_name going out of scope leaks the
storage it points to.

384        return res;


Looks like there are several return paths to out: that leak the
allocation of read_name.