From acc080d15dde820bd39eb55a04f9a09c7ef52e67 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 27 Oct 2020 10:42:56 +0000 Subject: [PATCH] afs: Fix tracing deref-before-check The patch dca54a7bbb8c: "afs: Add tracing for cell refcount and active user count" from Oct 13, 2020, leads to the following Smatch complaint: fs/afs/cell.c:596 afs_unuse_cell() warn: variable dereferenced before check 'cell' (see line 592) Fix this by moving the retrieval of the cell debug ID to after the check of the validity of the cell pointer. Reported-by: Dan Carpenter Fixes: dca54a7bbb8c ("afs: Add tracing for cell refcount and active user count") Signed-off-by: David Howells cc: Dan Carpenter --- fs/afs/cell.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/afs/cell.c b/fs/afs/cell.c index 52233fa6195f..887b673f6223 100644 --- a/fs/afs/cell.c +++ b/fs/afs/cell.c @@ -589,7 +589,7 @@ struct afs_cell *afs_use_cell(struct afs_cell *cell, enum afs_cell_trace reason) */ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_trace reason) { - unsigned int debug_id = cell->debug_id; + unsigned int debug_id; time64_t now, expire_delay; int u, a; @@ -604,6 +604,7 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr if (cell->vl_servers->nr_servers) expire_delay = afs_cell_gc_delay; + debug_id = cell->debug_id; u = atomic_read(&cell->ref); a = atomic_dec_return(&cell->active); trace_afs_cell(debug_id, u, a, reason);