[PATCH 5.11 118/210] hostfs: fix memory handling in follow_link()

Greg Kroah-Hartman
2021-04-12T09:31:40Z

From: Al Viro <viro@zeniv.linux.org.uk>

[ Upstream commit 7f6c411c9b50cfab41cc798e003eff27608c7016 ]

1) argument should not be freed in any case - the caller already has
it as ->s_fs_info (and uses it a lot afterwards)
2) allocate readlink buffer with kmalloc() - the caller has no way
to tell if it's got that (on absolute symlink) or a result of
kasprintf(). Sure, for SLAB and SLUB kfree() works on results of
kmem_cache_alloc(), but that's not documented anywhere, might change
in the future *and* is already not true for SLOB.

Fixes: 52b209f7b848 ("get rid of hostfs_read_inode()")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/hostfs/hostfs_kern.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index aea35459d390..07467ca0f71d 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -142,7 +142,7 @@ static char *follow_link(char *link)
char *name, *resolved, *end;
int n;

- name = __getname();
+ name = kmalloc(PATH_MAX, GFP_KERNEL);
if (!name) {
n = -ENOMEM;
goto out_free;
@@ -171,12 +171,11 @@ static char *follow_link(char *link)
goto out_free;
}

- __putname(name);
- kfree(link);
+ kfree(name);
return resolved;

out_free:
- __putname(name);
+ kfree(name);
return ERR_PTR(n);
}

--
2.30.2