6.11-stable review patch. If anyone has any objections, please let me know.
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From: Zizhi Wo wozizhi@huawei.com
[ Upstream commit 10c35abd35aa62c9aac56898ae0c63b4d7d115e5 ]
cachefiles_ondemand_fd_write_iter() function first aligns "pos" and "len" to block boundaries. When calling __cachefiles_write(), the aligned "pos" is passed in, but "len" is the original unaligned value(iter->count). Additionally, the returned length of the write operation is the modified "len" aligned by block size, which is unreasonable.
The alignment of "pos" and "len" is intended only to check whether the cache has enough space. But the modified len should not be used as the return value of cachefiles_ondemand_fd_write_iter() because the length we passed to __cachefiles_write() is the previous "len". Doing so would result in a mismatch in the data written on-demand. For example, if the length of the user state passed in is not aligned to the block size (the preread scene/DIO writes only need 512 alignment/Fault injection), the length of the write will differ from the actual length of the return.
To solve this issue, since the __cachefiles_prepare_write() modifies the size of "len", we pass "aligned_len" to __cachefiles_prepare_write() to calculate the free blocks and use the original "len" as the return value of cachefiles_ondemand_fd_write_iter().
Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie") Signed-off-by: Zizhi Wo wozizhi@huawei.com Link: https://lore.kernel.org/r/20241107110649.3980193-2-wozizhi@huawei.com Reviewed-by: David Howells dhowells@redhat.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/cachefiles/ondemand.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 470c966583850..bdd321017f1c4 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -61,7 +61,7 @@ static ssize_t cachefiles_ondemand_fd_write_iter(struct kiocb *kiocb, struct cachefiles_object *object = kiocb->ki_filp->private_data; struct cachefiles_cache *cache = object->volume->cache; struct file *file = object->file; - size_t len = iter->count; + size_t len = iter->count, aligned_len = len; loff_t pos = kiocb->ki_pos; const struct cred *saved_cred; int ret; @@ -70,7 +70,7 @@ static ssize_t cachefiles_ondemand_fd_write_iter(struct kiocb *kiocb, return -ENOBUFS;
cachefiles_begin_secure(cache, &saved_cred); - ret = __cachefiles_prepare_write(object, file, &pos, &len, len, true); + ret = __cachefiles_prepare_write(object, file, &pos, &aligned_len, len, true); cachefiles_end_secure(cache, saved_cred); if (ret < 0) return ret;