smb: client: fix request buffer leak in smb2_new_read_req()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-90125
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:17:04 UTC
Updated2026-09-17 17:17:04 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: smb: client: fix request buffer leak in smb2_new_read_req() smb2_new_read_req() allocates the request buffer with smb2_plain_req_init() but only publishes it to the caller with *buf = req at the very end of the function. Two error returns sit in between: rc = smb2_plain_req_init(SMB2_READ, io_parms->tcon, server, (void **) &req, total_len); if (rc) return rc; if (server == NULL) return -ECONNABORTED; [...] rdata->mr = smbd_register_mr(server->smbd_conn, &rdata->subreq.io_iter, true, need_invalidate); if (!rdata->mr) return -EAGAIN; On either of them the buffer is neither released nor handed back, so it is leaked. The caller cannot clean up after it: smb2_async_readv() does 'goto out' on a non-zero return, which skips the cifs_small_buf_release(buf) at async_readv_out, and buf has not been assigned at that point in any case. The write path has never had this problem. smb2_async_writev() registers the memory region inline and jumps to its release label instead of returning: wdata->mr = smbd_register_mr(...); if (!wdata->mr) { rc = -EAGAIN; goto async_writev_out; } Commit b7972092199f ("cifs: smbd: Retry on memory registration failure") changed both sides from -ENOBUFS to -EAGAIN in a single patch, which puts the two shapes next to each other. Only the -EAGAIN return is reachable in practice, because smb2_plain_req_init() calls smb2_reconnect() first and that already fails with -EIO when server is NULL, before anything is allocated. Both returns are given the same treatment here rather than leaving one of them correct only by accident. Because -EAGAIN is a replayable error, the failure also reaches the retry block at the end of smb2_async_readv(), which marks the subrequest NETFS_SREQ_NEED_RETRY, so a failing registration can be retried rather than ending the I/O, and every attempt that reaches it leaks another buffer. smb2_should_replay() short-circuits on tcon->retry, so on a hard mount the attempt count is not bounded by the retrans setting. Only the asynchronous read path is affected. The synchronous SMB2_read() caller passes rdata == NULL and the memory registration block is guarded on rdata. The memory registration failure path was pointed out by the Sashiko AI reviewer while it was reviewing an unrelated patch to smb2_async_readv().

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected bd3dcc6a22a9186ed78da51ce09e889803552189 58066940076b90c16e821fd6f9767cd979cbdb5e git Not specified
CNA Linux Linux affected bd3dcc6a22a9186ed78da51ce09e889803552189 12092ed28434bf41e08d41e3c5269eb6b337fc02 git Not specified
CNA Linux Linux affected bd3dcc6a22a9186ed78da51ce09e889803552189 442c5f1358ced0d4e716778ac06f1e323a7e4f21 git Not specified
CNA Linux Linux affected bd3dcc6a22a9186ed78da51ce09e889803552189 73f6bdb0380486ab37fe12cd74de20abfaf5d3ae git Not specified
CNA Linux Linux affected bd3dcc6a22a9186ed78da51ce09e889803552189 deb6468f4164640e4dc875f008aa449cf55987a5 git Not specified
CNA Linux Linux affected 4.16 Not specified
CNA Linux Linux unaffected 4.16 semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.110 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/deb6468f4164640e4dc875f008aa449cf55987a5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/12092ed28434bf41e08d41e3c5269eb6b337fc02 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/58066940076b90c16e821fd6f9767cd979cbdb5e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/442c5f1358ced0d4e716778ac06f1e323a7e4f21 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/73f6bdb0380486ab37fe12cd74de20abfaf5d3ae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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