CVE-2026-90125
smb: client: fix request buffer leak in smb2_new_read_req()
Published Sep 17, 2026
CVSS n/a
EPSS < 1%
KEV · Not listed
Description
In 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().
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().
Affected Products
-
CVE record
-
NVD configurations
No data
-
Red Hat packages
No data
-
OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
|
No data.
No data.
| Vendor | Product | Versions | ||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel |
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| Linux | Linux Kernel |
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Remediation
Tracking
Advisories
| Source | ID | Title |
|---|---|---|
 Debian DLA |
DLA-4817-1 | linux-6.12 security update |
 Debian DSA |
DSA-6528-1 | linux security update |
 Ubuntu USN |
USN-9019-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9020-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9022-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9023-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9024-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9025-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9026-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9039-1 | Linux kernel (Azure CVM) vulnerabilities |
| Ubuntu USN |
USN-9040-1 | Linux kernel (Low Latency NVIDIA) vulnerabilities |
| Ubuntu USN |
USN-9066-1 | Linux kernel (HWE) vulnerabilities |
| Ubuntu USN |
USN-9091-1 | Linux kernel (NVIDIA Tegra) vulnerabilities |
Metrics
No CVSS v4.0
No CVSS v3.1
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.206% probability within 30 days)
Key SSVC decision points have not yet been added.
References
History
Oct 30, 2026 12:45 PM
Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Sep 19, 2026 12:15 AM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-401 CWE-772 |
Sep 17, 2026 4:30 PM
Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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(). | |
| Title | smb: client: fix request buffer leak in smb2_new_read_req() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
