[PATCH net-next v3 0/2] ptp: reject frequency adjustments that overflow scaled_ppm_to_ppb()

[Deep Shah <deepshah146@gmail.com>]

ptp_clock_adjtime() validates an ADJ_FREQUENCY request by converting
tx->freq to ppb and comparing it against ops->max_adj. On 64-bit systems
that conversion can overflow s64 and wrap the result back into range, so
a crafted tx->freq bypasses the check and reaches ->adjfine() unclamped.

No real user space asks for such a frequency, so this is hardening rather
than a fix anyone is waiting on, and it is targeted at net-next with no
Fixes tag per Jakub's feedback on v2.

Patch 1 rejects the overflow in ptp_clock_adjtime().
Patch 2 adds a regression test that crafts struct timex.freq directly
(testptp's int-ppb path cannot express the value) and confirms it is
rejected with -ERANGE.

Changes in v3:
- retarget at net-next and drop the Fixes tag (Jakub Kicinski)
- patch 1: unchanged
- patch 2:
  - cast the test value to the type of tx.freq rather than guarding on
    __SIZEOF_LONG__, which skipped the assignment on x32 and other
    y2038 configurations and failed the test there (Simon Horman)
  - add the built binary to .gitignore

Changes in v2:
- patch 1: added Reviewed-by from Vadim Fedorenko.
- patch 2 (all from Simon Horman's review):
  - cast fd to unsigned before the shift in FD_TO_CLOCKID (UBSan)
  - avoid a -Woverflow warning on 32-bit
  - save and restore the clock frequency
  - skip instead of fail on -EBUSY (free-running clock)

Link to v1:
https://lore.kernel.org/netdev/20260712040922.6403-1-deepshah146@gmail.com/
Link to v2:
https://lore.kernel.org/netdev/20260721014256.1876-1-deepshah146@gmail.com/

Deep Shah (2):
  ptp: reject frequency adjustments that overflow scaled_ppm_to_ppb()
  selftests: ptp: add a regression test for the frequency adjustment
    overflow

 drivers/ptp/ptp_clock.c                       |  14 ++-
 tools/testing/selftests/ptp/.gitignore        |   1 +
 tools/testing/selftests/ptp/Makefile          |   2 +-
 .../testing/selftests/ptp/ptp_freq_overflow.c | 101 ++++++++++++++++++
 4 files changed, 116 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/ptp/ptp_freq_overflow.c


base-commit: 69963a0678a347d57c4ac8b16939dba216eb95ce
-- 
2.43.0