CVE-2026-43388

mm/damon/core: clear walk_control on inactive context in damos_walk()

Published May 8, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: clear walk_control on inactive context in damos_walk()

damos_walk() sets ctx->walk_control to the caller-provided control
structure before checking whether the context is running. If the context
is inactive (damon_is_running() returns false), the function returns
-EINVAL without clearing ctx->walk_control. This leaves a dangling
pointer to a stack-allocated structure that will be freed when the caller
returns.

This is structurally identical to the bug fixed in commit f9132fbc2e83
("mm/damon/core: remove call_control in inactive contexts") for
damon_call(), which had the same pattern of linking a control object and
returning an error without unlinking it.

The dangling walk_control pointer can cause:
1. Use-after-free if the context is later started and kdamond
   dereferences ctx->walk_control (e.g., in damos_walk_cancel()
   which writes to control->canceled and calls complete())
2. Permanent -EBUSY from subsequent damos_walk() calls, since the
   stale pointer is non-NULL

Nonetheless, the real user impact is quite restrictive. The
use-after-free is impossible because there is no damos_walk() callers who
starts the context later. The permanent -EBUSY can actually confuse
users, as DAMON is not running. But the symptom is kept only while the
context is turned off. Turning it on again will make DAMON internally
uses a newly generated damon_ctx object that doesn't have the invalid
damos_walk_control pointer, so everything will work fine again.

Fix this by clearing ctx->walk_control under walk_control_lock before
returning -EINVAL, mirroring the fix pattern from f9132fbc2e83.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

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History
Type Values Removed Values Added
Weaknesses CWE-416
CPEs cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: clear walk_control on inactive context in damos_walk() damos_walk() sets ctx->walk_control to the caller-provided control structure before checking whether the context is running. If the context is inactive (damon_is_running() returns false), the function returns -EINVAL without clearing ctx->walk_control. This leaves a dangling pointer to a stack-allocated structure that will be freed when the caller returns. This is structurally identical to the bug fixed in commit f9132fbc2e83 ("mm/damon/core: remove call_control in inactive contexts") for damon_call(), which had the same pattern of linking a control object and returning an error without unlinking it. The dangling walk_control pointer can cause: 1. Use-after-free if the context is later started and kdamond    dereferences ctx->walk_control (e.g., in damos_walk_cancel()    which writes to control->canceled and calls complete()) 2. Permanent -EBUSY from subsequent damos_walk() calls, since the    stale pointer is non-NULL Nonetheless, the real user impact is quite restrictive. The use-after-free is impossible because there is no damos_walk() callers who starts the context later. The permanent -EBUSY can actually confuse users, as DAMON is not running. But the symptom is kept only while the context is turned off. Turning it on again will make DAMON internally uses a newly generated damon_ctx object that doesn't have the invalid damos_walk_control pointer, so everything will work fine again. Fix this by clearing ctx->walk_control under walk_control_lock before returning -EINVAL, mirroring the fix pattern from f9132fbc2e83.
Title mm/damon/core: clear walk_control on inactive context in damos_walk()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
May 11, 2026, 10:23 PM
Reserved
May 1, 2026, 2:12 PM
Status
Analyzed
Published
May 8, 2026, 3:16 PM
Modified
Nov 11, 2026, 8:10 PM
Severity
Public date
May 8, 2026, 12:00 AM