CVE-2026-90277

Summary

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

md/md-llbitmap: prevent create failure bitmap UAF

llbitmap_create() publishes mddev->bitmap before reading the bitmap superblock. This is needed because llbitmap_read_sb() can initialize a new bitmap and flush it through helpers that use mddev->bitmap.

If llbitmap_read_sb() fails, the old cleanup dropped bitmap_info.mutex and freed llbitmap before clearing mddev->bitmap. Readers such as /proc/mdstat rely on bitmap_info.mutex to keep the bitmap pointer stable while collecting bitmap stats, so they could observe the stale pointer after the failed create path released the mutex.

Clear mddev->bitmap while still holding bitmap_info.mutex, then free the failed llbitmap after dropping the mutex. This makes mutex-protected readers see either a live bitmap or no bitmap.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/930cc4f1af5a1afcd545a6ba00e38921ff8401e0
• https://git.kernel.org/stable/c/2f0722435ce3a844dbb66b9bb0a18229dcc8739c
• https://git.kernel.org/stable/c/2116c2f0a0e547615886900e2ed8c529c016499b

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