CVE-2026-46253

Description

In the Linux kernel, the following vulnerability has been resolved: pstore/ram: fix buffer overflow in persistent_ram_save_old() persistent_ram_save_old() can be called multiple times for the same persistent_ram_zone (e.g., via ramoops_pstore_read -> ramoops_get_next_prz for PSTORE_TYPE_DMESG records). Currently, the function only allocates prz->old_log when it is NULL, but it unconditionally updates prz->old_log_size to the current buffer size and then performs memcpy_fromio() using this new size. If the buffer size has grown since the first allocation (which can happen across different kernel boot cycles), this leads to: 1. A heap buffer overflow (OOB write) in the memcpy_fromio() calls 2. A subsequent OOB read when ramoops_pstore_read() accesses the buffer using the incorrect (larger) old_log_size The KASAN splat would look similar to: BUG: KASAN: slab-out-of-bounds in ramoops_pstore_read+0x... Read of size N at addr ... by task ... The conditions are likely extremely hard to hit: 0. Crash with a ramoops write of less-than-record-max-size bytes. 1. Reboot: ramoops registers, pstore_get_records(0) reads old crash, allocates old_log with size X 2. Crash handler registered, timer started (if pstore_update_ms >= 0) 3. Oops happens (non-fatal, system continues) 4. pstore_dump() writes oops via ramoops_pstore_write() size Y (>X) 5. pstore_new_entry = 1, pstore_timer_kick() called 6. System continues running (not a panic oops) 7. Timer fires after pstore_update_ms milliseconds 8. pstore_timefunc() → schedule_work() → pstore_dowork() → pstore_get_records(1) 9. ramoops_get_next_prz() → persistent_ram_save_old() 10. buffer_size() returns Y, but old_log is X bytes 11. Y > X: memcpy_fromio() overflows heap Requirements: - a prior crash record exists that did not fill the record size (almost impossible since the crash handler writes as much as it can possibly fit into the record, capped by max record size and the kmsg buffer almost always exceeds the max record size) - pstore_update_ms >= 0 (disabled by default) - Non-fatal oops (system survives) Free and reallocate the buffer when the new size differs from the previously allocated size. This ensures old_log always has sufficient space for the data being copied.

PUBLISHED Reserved 2026-05-13 | Published 2026-06-03 | Updated 2026-06-05 | Assigner Linux

Product status

References

git.kernel.org/...c/58bda5a1d1ee98254383ef34f76b2c35140513ea

git.kernel.org/...c/06d2c8bd108cea503f6f6e13e47495ed1085275f

git.kernel.org/...c/2fa9a047c6a50ec80c3890dd623b85e237f0d1fd

git.kernel.org/...c/cff0ef043e16feb5a02307c8f9d0117a96c5587c

git.kernel.org/...c/9a6fc69a570c0780834246d52c856cc3dbc2605f

git.kernel.org/...c/4f73486ca822305c1cf5b8ebc0b53a6ab3801a81

git.kernel.org/...c/7cfe964e61c0ab667abd5f5b68e0acbf783efa4f

git.kernel.org/...c/5669645c052f235726a85f443769b6fc02f66762

cve.org (CVE-2026-46253)

nvd.nist.gov (CVE-2026-46253)

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