From: Kuniyuki Iwashima Date: Sat, 24 Jan 2026 04:18:40 +0000 (+0000) Subject: nfsd: Fix cred ref leak in nfsd_nl_threads_set_doit(). X-Git-Tag: ceph-for-7.0-rc4~60^2~2 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=1cb968a2013ffa8112d52ebe605009ea1c6a582c;p=ceph-client.git nfsd: Fix cred ref leak in nfsd_nl_threads_set_doit(). syzbot reported memory leak of struct cred. [0] nfsd_nl_threads_set_doit() passes get_current_cred() to nfsd_svc(), but put_cred() is not called after that. The cred is finally passed down to _svc_xprt_create(), which calls get_cred() with the cred for struct svc_xprt. The ownership of the refcount by get_current_cred() is not transferred to anywhere and is just leaked. nfsd_svc() is also called from write_threads(), but it does not bump file->f_cred there. nfsd_nl_threads_set_doit() is called from sendmsg() and current->cred does not go away. Let's use current_cred() in nfsd_nl_threads_set_doit(). [0]: BUG: memory leak unreferenced object 0xffff888108b89480 (size 184): comm "syz-executor", pid 5994, jiffies 4294943386 hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 369454a7): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x412/0x580 mm/slub.c:5270 prepare_creds+0x22/0x600 kernel/cred.c:185 copy_creds+0x44/0x290 kernel/cred.c:286 copy_process+0x7a7/0x2870 kernel/fork.c:2086 kernel_clone+0xac/0x6e0 kernel/fork.c:2651 __do_sys_clone+0x7f/0xb0 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 924f4fb003ba ("NFSD: convert write_threads to netlink command") Cc: stable@vger.kernel.org Reported-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69744674.a00a0220.33ccc7.0000.GAE@google.com/ Tested-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Signed-off-by: Kuniyuki Iwashima Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index 89fe2c0e8d44..43ced6b0e197 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1647,7 +1647,7 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info) if (attr) nn->min_threads = nla_get_u32(attr); - ret = nfsd_svc(nrpools, nthreads, net, get_current_cred(), scope); + ret = nfsd_svc(nrpools, nthreads, net, current_cred(), scope); if (ret > 0) ret = 0; out_unlock: