From 71d3850bf1e9458ed6a6119abe084e253128dee5 Mon Sep 17 00:00:00 2001 From: Jan Harkes Date: Wed, 27 Sep 2017 15:52:12 -0400 Subject: [PATCH] coda: fix 'kernel memory exposure attempt' in fsync commit d337b66a4c52c7b04eec661d86c2ef6e168965a2 upstream. When an application called fsync on a file in Coda a small request with just the file identifier was allocated, but the declared length was set to the size of union of all possible upcall requests. This bug has been around for a very long time and is now caught by the extra checking in usercopy that was introduced in Linux-4.8. The exposure happens when the Coda cache manager process reads the fsync upcall request at which point it is killed. As a result there is nobody servicing any further upcalls, trapping any processes that try to access the mounted Coda filesystem. Signed-off-by: Jan Harkes Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/coda/upcall.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/coda/upcall.c b/fs/coda/upcall.c index a37f003530d7..1175a1722411 100644 --- a/fs/coda/upcall.c +++ b/fs/coda/upcall.c @@ -447,8 +447,7 @@ int venus_fsync(struct super_block *sb, struct CodaFid *fid) UPARG(CODA_FSYNC); inp->coda_fsync.VFid = *fid; - error = coda_upcall(coda_vcp(sb), sizeof(union inputArgs), - &outsize, inp); + error = coda_upcall(coda_vcp(sb), insize, &outsize, inp); CODA_FREE(inp, insize); return error;