[SRU][N][PATCH 0/1] CVE-2025-21887

[Manuel Diewald]

https://ubuntu.com/security/CVE-2025-21887

SRU Justification:

[Impact]

In the Linux kernel, the following vulnerability has been resolved:

ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up

The issue was caused by dput(upper) being called before
ovl_dentry_update_reval(), while upper->d_flags was still accessed in
ovl_dentry_remote(). Move dput(upper) after its last use to prevent
use-after-free.

[Fix]

Plucky: Not affected
Noble:  Clean cherry-pick from mainline
Jammy:  Fixed with upstream stable update v5.15.179 (LP: #2106026)
Focal:  Not affected
Bionic: Not affected
Xenial: Not affected
Trusty: Not affected

[Test Plan]

Compile-tested only.

[Where problems could occur]

Problems with the patch would be limited to overlayfs and manifest as
unexpected behavior involving files.


Vasiliy Kovalev (1):
  ovl: fix UAF in ovl_dentry_update_reval by moving dput() in
    ovl_link_up

 fs/overlayfs/copy_up.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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2.34.1