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| author | Eric Biggers <ebiggers@google.com> | 2018-12-28 00:34:43 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-28 12:11:47 -0800 |
| commit | ca880420665dbc8beec3693bee9f5eccb89de4a6 (patch) | |
| tree | 7255c489175110780706a7eaf04fe8f0f34611b5 /fs/userfaultfd.c | |
| parent | 66f71da9dd38af17dc17209cdde7987d4679a699 (diff) | |
| download | linux-ca880420665dbc8beec3693bee9f5eccb89de4a6.tar.gz linux-ca880420665dbc8beec3693bee9f5eccb89de4a6.tar.bz2 linux-ca880420665dbc8beec3693bee9f5eccb89de4a6.zip | |
userfaultfd: convert userfaultfd_ctx::refcount to refcount_t
Reference counters should use refcount_t rather than atomic_t, since the
refcount_t implementation can prevent overflows, reducing the
exploitability of reference leak bugs. userfaultfd_ctx::refcount is a
reference counter with the usual semantics, so convert it to refcount_t.
Note: I replaced the BUG() on incrementing a 0 refcount with just
refcount_inc(), since part of the semantics of refcount_t is that that
incrementing a 0 refcount is not allowed; with CONFIG_REFCOUNT_FULL,
refcount_inc() already checks for it and warns.
Link: http://lkml.kernel.org/r/20181115003916.63381-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/userfaultfd.c')
| -rw-r--r-- | fs/userfaultfd.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 59dc28047030..e211b99d33c4 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -53,7 +53,7 @@ struct userfaultfd_ctx { /* a refile sequence protected by fault_pending_wqh lock */ struct seqcount refile_seq; /* pseudo fd refcounting */ - atomic_t refcount; + refcount_t refcount; /* userfaultfd syscall flags */ unsigned int flags; /* features requested from the userspace */ @@ -140,8 +140,7 @@ out: */ static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) { - if (!atomic_inc_not_zero(&ctx->refcount)) - BUG(); + refcount_inc(&ctx->refcount); } /** @@ -154,7 +153,7 @@ static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) */ static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) { - if (atomic_dec_and_test(&ctx->refcount)) { + if (refcount_dec_and_test(&ctx->refcount)) { VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); @@ -686,7 +685,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) return -ENOMEM; } - atomic_set(&ctx->refcount, 1); + refcount_set(&ctx->refcount, 1); ctx->flags = octx->flags; ctx->state = UFFD_STATE_RUNNING; ctx->features = octx->features; @@ -1927,7 +1926,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags) if (!ctx) return -ENOMEM; - atomic_set(&ctx->refcount, 1); + refcount_set(&ctx->refcount, 1); ctx->flags = flags; ctx->features = 0; ctx->state = UFFD_STATE_WAIT_API; |