btrfs: check if root is readonly when setting posix acl

Summary

In the Linux kernel, the following vulnerability has been resolved: btrfs: check if root is readonly when setting posix acl For a filesystem which has btrfs read-only property set to true, all write operations including acl and xattr should be denied. However, acl can still be set even if btrfs ro property is true. This happens because no function on the set_acl code path checks the root is readonly or not. It was checked in btrfs_setxattr_trans() but got removed in commit 353c2ea735e4 ("btrfs: remove redundant readonly root check in btrfs_setxattr_trans") That commit didn't check if all the callers properly check the root's read-only flag. A previous fix is commit b51111271b03 ("btrfs: check if root is readonly while setting security xattr"). Always check if the root is read-only before performing the set acl operation.

Timeline

1. Sep 17, 2026, 4:08 PM UTCCVE published
2. Oct 21, 2026, 12:50 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 353c2ea735e4b54fb6250861e67b51b1bcb47198 · fixed in 20b2c2f3316e82a76ae3358c0bd45824f50f3fd5; From 353c2ea735e4b54fb6250861e67b51b1bcb47198 · fixed in dc3a6e90a0a6350a6d43fed9f005f54171809580; From 353c2ea735e4b54fb6250861e67b51b1bcb47198 · fixed in ce8103676f4d4b13e1f087fcfb34f80774d30be2; From 353c2ea735e4b54fb6250861e67b51b1bcb47198 · fixed in d5602f96ff1e266f069b4d0d94f441050e057e06; From 353c2ea735e4b54fb6250861e67b51b1bcb47198 · fixed in 01c2f41fc441f75b3f9326443372faceb1cb6638

• Linux Linux

  5.2

• KernelLinux

  From 5.2.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.6

References 5