shmem: fix recovery on rename failures

Summary

In the Linux kernel, the following vulnerability has been resolved: shmem: fix recovery on rename failures maple_tree insertions can fail if we are seriously short on memory; simple_offset_rename() does not recover well if it runs into that. The same goes for simple_offset_rename_exchange(). Moreover, shmem_whiteout() expects that if it succeeds, the caller will progress to d_move(), i.e. that shmem_rename2() won't fail past the successful call of shmem_whiteout(). Not hard to fix, fortunately - mtree_store() can't fail if the index we are trying to store into is already present in the tree as a singleton. For simple_offset_rename_exchange() that's enough - we just need to be careful about the order of operations. For simple_offset_rename() solution is to preinsert the target into the tree for new_dir; the rest can be done without any potentially failing operations. That preinsertion has to be done in shmem_rename2() rather than in simple_offset_rename() itself - otherwise we'd need to deal with the possibility of failure after successful shmem_whiteout().

Timeline

1. Jan 13, 2026, 3:31 PM UTCCVE published
2. Oct 21, 2026, 12:38 PM UTCRecord last updated

Affected versions

• Linux Linux

  From a2e459555c5f9da3e619b7e47a63f98574dc75f1 · fixed in 8fdbc6f9a994eb327868a4aa74a58953f31a2d0f; From a2e459555c5f9da3e619b7e47a63f98574dc75f1 · fixed in 4b0fe71fb3965d0db83cdfc2f4fe0b3227d70113; From a2e459555c5f9da3e619b7e47a63f98574dc75f1 · fixed in 4642686699a46718d7f2fb5acd1e9d866a9d9cca; From a2e459555c5f9da3e619b7e47a63f98574dc75f1 · fixed in e1b4c6a58304fd490124cc2b454d80edc786665c

• Linux Linux

  6.6

• KernelLinux

  From 6.6.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.64; From 6.13.0 · fixed in 6.18.3

References 4