CVE-2026-99156scsi: st: Fix use-after-free race between st_remove() and st_open()

Official description

In the Linux kernel, the following vulnerability has been resolved: scsi: st: Fix use-after-free race between st_remove() and st_open() st_remove() drops the probe reference on the scsi_tape with kref_put() and only afterwards removes its index from st_index_idr. If that was the last reference, scsi_tape_release() frees the structure while it is still published in the idr. scsi_tape_get(), called from st_open(), looks up the tape in st_index_idr and takes a reference under st_ref_mutex and st_index_lock. remove_cdevs() does not wait for opens that are already past chrdev_open(), so an open that is blocked on st_ref_mutex while st_remove() holds it can take the mutex as soon as st_remove() drops it, find the freed tpnt in the idr and call kref_get() on it: BUG: KASAN: slab-use-after-free in st_open Write of size 4 ... st_open (drivers/scsi/st.c:254 drivers/scsi/st.c:1291) chrdev_open ... Freed by task ...: kfree st_remove (drivers/scsi/st.c:4512) Remove the index from the idr before dropping the reference, all under st_ref_mutex. A concurrent scsi_tape_get() now either runs first and holds a valid reference that keeps the tape alive, or runs afterwards and finds nothing, so st_open() fails with -ENXIO. This restores the ordering st_remove() had before the conversion to st_index_idr, where the tape was unpublished from scsi_tapes[] before the final kref_put().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/7d7f9d2ee4b0841f3eba9fa3627044ad329428de
• https://git.kernel.org/stable/c/d9517fc39ec3ee13eadefdc17f45300f7d23ed8c
• https://git.kernel.org/stable/c/e7a5da4a4820210aa7d7cd8e6eb25aabe9e5b5a7
• https://git.kernel.org/stable/c/00ff1128123d4bdfacd28d68fb4b6e6f657a3648
• https://git.kernel.org/stable/c/5ef230f734e0d23db007c8405f38b7e226740084
• https://git.kernel.org/stable/c/a1647b653549ff29f0422a63eabf329b842f3822
• https://git.kernel.org/stable/c/18a0e3733ce38718688e813e5e2d1106bd4830e5
• https://git.kernel.org/stable/c/71caf7f84bd62a4bf91cc95abd2de690afb8d15f