This is a note to let you know that I've just added the patch titled cred: allow get_cred() and put_cred() to be given NULL. to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cred-allow-get_cred-and-put_cred-to-be-given-null.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From f06bc03339ad4c1baa964a5f0606247ac1c3c50b Mon Sep 17 00:00:00 2001 From: NeilBrown <neilb@xxxxxxxx> Date: Mon, 3 Dec 2018 11:30:30 +1100 Subject: cred: allow get_cred() and put_cred() to be given NULL. From: NeilBrown <neilb@xxxxxxxx> commit f06bc03339ad4c1baa964a5f0606247ac1c3c50b upstream. It is common practice for helpers like this to silently, accept a NULL pointer. get_rpccred() and put_rpccred() used by NFS act this way and using the same interface will ease the conversion for NFS, and simplify the resulting code. Signed-off-by: NeilBrown <neilb@xxxxxxxx> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/cred.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -234,7 +234,7 @@ static inline struct cred *get_new_cred( * @cred: The credentials to reference * * Get a reference on the specified set of credentials. The caller must - * release the reference. + * release the reference. If %NULL is passed, it is returned with no action. * * This is used to deal with a committed set of credentials. Although the * pointer is const, this will temporarily discard the const and increment the @@ -245,6 +245,8 @@ static inline struct cred *get_new_cred( static inline const struct cred *get_cred(const struct cred *cred) { struct cred *nonconst_cred = (struct cred *) cred; + if (!cred) + return cred; validate_creds(cred); nonconst_cred->non_rcu = 0; return get_new_cred(nonconst_cred); @@ -255,7 +257,7 @@ static inline const struct cred *get_cre * @cred: The credentials to release * * Release a reference to a set of credentials, deleting them when the last ref - * is released. + * is released. If %NULL is passed, nothing is done. * * This takes a const pointer to a set of credentials because the credentials * on task_struct are attached by const pointers to prevent accidental @@ -265,9 +267,11 @@ static inline void put_cred(const struct { struct cred *cred = (struct cred *) _cred; - validate_creds(cred); - if (atomic_dec_and_test(&(cred)->usage)) - __put_cred(cred); + if (cred) { + validate_creds(cred); + if (atomic_dec_and_test(&(cred)->usage)) + __put_cred(cred); + } } /** Patches currently in stable-queue which might be from neilb@xxxxxxxx are queue-4.9/cred-allow-get_cred-and-put_cred-to-be-given-null.patch