secretmem: Prevent secretmem_users from wrapping to zero
Commit 110860541f44 ("mm/secretmem: use refcount_t instead of atomic_t")
attempted to fix the problem of secretmem_users wrapping to zero and
allowing suspend once again.
But it was reverted in commit 87066fdd2e30 ("Revert 'mm/secretmem: use
refcount_t instead of atomic_t'") because of the problems it caused - a
refcount_t was not semantically the right type to use.
Instead prevent secretmem_users from wrapping to zero by forbidding new
users if the number of users has wrapped from positive to negative.
This stops a long way short of reaching the necessary 4 billion users
where it wraps to zero again, so there's no need to be clever with
special anti-wrap types or checking the return value from atomic_inc().
Signed-off-by: Matthew Wilcox (Oracle) <firstname.lastname@example.org>
Cc: Jordy Zomer <email@example.com>
Cc: Kees Cook <firstname.lastname@example.org>,
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Mike Rapoport <email@example.com>
Cc: Andrew Morton <firstname.lastname@example.org>
Signed-off-by: Linus Torvalds <email@example.com>
1 file changed