[Minios-devel] [UNIKRAFT PATCH] lib/{ramfs, vfscore}: fix invalid error codes

[Hugo Lefeuvre <hle@xxxxxxxxxx>]

+ ramfs_truncate and ramfs_write currently return EIO upon failing to
  allocate memory for ramfs_node file data buffers. In the majority of
  cases this is caused by the allocator running out-of-memory, so
  returning ENOMEM seems more appropriate. This avoids OOM issues hiding
  behind obscure I/O error messages.

+ vfscore_vget returns 1 if the vnode was found in cache, 0 otherwise.

  If we fall back to allocating a new vnode (vn_lookup returned NULL)
  then the vnode was not found in cache and it does not make sense to
  return anything else than 0.

  In particular, this line is reached if VFS_VGET fails, meaning that
  error will systematically be > 0. Since most calls to vfscore_vget
  check for > 0 instead of == 1, they will assume that the vnode was
  found in cache and dereference vpp without previously checking it,
  causing a NULL pointer dereference.

  This is not an issue for the moment since all vfs_vget implementations
  are linked to vfscore_nullop, but might become an issue in the future
  when those will be implemented.

Signed-off-by: Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>
---
 lib/ramfs/ramfs_vnops.c | 4 ++--
 lib/vfscore/vnode.c     | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/ramfs/ramfs_vnops.c b/lib/ramfs/ramfs_vnops.c
index 6eca9b2..2ea2626 100644
--- a/lib/ramfs/ramfs_vnops.c
+++ b/lib/ramfs/ramfs_vnops.c
@@ -357,7 +357,7 @@ ramfs_truncate(struct vnode *vp, off_t length)
                new_size = round_pgup(length);
                new_buf = malloc(new_size);
                if (!new_buf)
-                       return EIO;
+                       return ENOMEM;
                if (np->rn_size != 0) {
                        memcpy(new_buf, np->rn_buf, vp->v_size);
                        if (np->rn_owns_buf)
@@ -473,7 +473,7 @@ ramfs_write(struct vnode *vp, struct uio *uio, int ioflag)
                        void *new_buf = calloc(1, new_size);
 
                        if (!new_buf)
-                               return EIO;
+                               return ENOMEM;
                        if (np->rn_size != 0) {
                                memcpy(new_buf, np->rn_buf, vp->v_size);
                                if (np->rn_owns_buf)
diff --git a/lib/vfscore/vnode.c b/lib/vfscore/vnode.c
index 6b5ea12..f3f1644 100644
--- a/lib/vfscore/vnode.c
+++ b/lib/vfscore/vnode.c
@@ -209,7 +209,7 @@ vfscore_vget(struct mount *mp, uint64_t ino, struct vnode 
**vpp)
        if ((error = VFS_VGET(mp, vp)) != 0) {
                VNODE_UNLOCK();
                free(vp);
-               return error;
+               return 0;
        }
        vfs_busy(vp->v_mount);
        uk_mutex_lock(&vp->v_lock);
-- 
2.25.0

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