On Thu, Nov 18, 2021 at 4:34 PM Hanna Reitz <hre...@redhat.com> wrote:
On 16.11.21 13:57, Daniella Lee wrote:
> Function vvfat_open called function enable_write_target and
init_directories,
> and these functions malloc new memory for
BDRVVVFATState::qcow_filename,
> BDRVVVFATState::used_clusters, and BDRVVVFATState::cluster_buff.
>
> When the specified folder does not exist ,it may contains memory
leak.
> After init_directories function is executed, the vvfat_open
return -EIO,
> and bdrv_open_driver goto label open_failed,
> the program use g_free(bs->opaque) to release BDRVVVFATState struct
> without members mentioned.
>
> command line:
> qemu-system-x86_64 -hdb <vdisk qcow file> -usb -device
usb-storage,drive=fat16
> -drive file=fat:rw:fat-type=16:"<path of a host folder does not
exist>",
> id=fat16,format=raw,if=none
>
> enable_write_target called:
> (gdb) bt
> #0 enable_write_target (bs=0x555556f9f000, errp=0x7fffffffd780)
> at ../block/vvfat.c:3114
> #1 vvfat_open (bs=0x555556f9f000, options=0x555556fa45d0,
> flags=155650, errp=0x7fffffffd780) at ../block/vvfat.c:1236
> #2 bdrv_open_driver (bs=0x555556f9f000, drv=0x555556c47920
<bdrv_vvfat>,
> node_name=0x0, options=0x555556fa45d0, open_flags=155650,
> errp=0x7fffffffd890) at ../block.c:1558
> #3 bdrv_open_common (bs=0x555556f9f000, file=0x0,
options=0x555556fa45d0,
> errp=0x7fffffffd890) at ../block.c:1852
> #4 bdrv_open_inherit (filename=0x555556f73310 "fat:rw:<dirNone>",
> reference=0x0, options=0x555556fa45d0, flags=40962,
parent=0x555556f98cd0,
> child_class=0x555556b1d6a0 <child_of_bds>, child_role=19,
> errp=0x7fffffffda90) at ../block.c:3779
> #5 bdrv_open_child_bs (filename=0x555556f73310 "fat:rw:<dirNone>",
> options=0x555556f9cfc0, bdref_key=0x555556239bb8 "file",
> parent=0x555556f98cd0, child_class=0x555556b1d6a0
<child_of_bds>,
> child_role=19, allow_none=true, errp=0x7fffffffda90) at
../block.c:3419
> #6 bdrv_open_inherit (filename=0x555556f73310 "fat:rw:<dirNone>",
> reference=0x0, options=0x555556f9cfc0, flags=8194, parent=0x0,
> child_class=0x0, child_role=0, errp=0x555556c98c40
<error_fatal>)
> at ../block.c:3726
> #7 bdrv_open (filename=0x555556f73310 "fat:rw:<dirNone>",
reference=0x0,
> options=0x555556f757b0, flags=0, errp=0x555556c98c40
<error_fatal>)
> at ../block.c:3872
> #8 blk_new_open (filename=0x555556f73310 "fat:rw:<dirNone>",
reference=0x0,
> options=0x555556f757b0, flags=0, errp=0x555556c98c40
<error_fatal>)
> at ../block/block-backend.c:436
> #9 blockdev_init (file=0x555556f73310 "fat:rw:<dirNone>",
> bs_opts=0x555556f757b0, errp=0x555556c98c40 <error_fatal>)
> at ../blockdev.c:608
> #10 drive_new (all_opts=0x555556d2b700, block_default_type=IF_IDE,
> errp=0x555556c98c40 <error_fatal>) at ../blockdev.c:992
> ......
>
> Signed-off-by: Daniella Lee <daniellalee...@gmail.com>
> ---
> block/vvfat.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
Hi,
Thanks for your patch! Yes, that makes sense.
I believe there are some issues that should be addressed, though:
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 05e78e3c27..454a74c5d5 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1280,7 +1280,22 @@ static int vvfat_open(BlockDriverState
*bs, QDict *options, int flags,
> qemu_co_mutex_init(&s->lock);
>
> ret = 0;
> +
> + qemu_opts_del(opts);
> + return ret;
Optional: I’d drop the `ret = 0;` line and just `return 0;` here.
> fail:
> + if(s->qcow_filename) {
Our coding style requires a space between `if` and the opening
parenthesis.
> + g_free(s->qcow_filename);
`g_free()` checks whether the parameter given to it is `NULL`, and if
so, performs a no-op. So checking whether `s->qcow_filename != NULL`
before calling `g_free()` is not necessary.
We have a script under scripts/checkpatch.pl
<http://checkpatch.pl> that takes patch files as
input and checks whether they conform to our coding style. It’s
really
helpful, for example in these two cases it does report the issues.
> + s->qcow_filename = NULL;
> + }
> + if(s->cluster_buffer) {
> + g_free(s->cluster_buffer);
> + s->cluster_buffer = NULL;
> + }
> + if(s->used_clusters) {
> + g_free(s->used_clusters);
`s->used_clusters` is allocated with `calloc()`, so it can’t be freed
with `g_free()`. But you’re right, it should be `g_free()`-able,
so the
fix is to have `enable_write_target()` allocate it with
`g_malloc0(size)`.
(And this made me notice that we free neither `s->used_clusters` nor
`s->qcow_filename` in vvfat_close()... Oops.)
> + s->used_clusters = NULL;
> + }
> qemu_opts_del(opts);
> return ret;
> }
Finally, `enable_write_target()` frees `s->qcow_filename` on error.
That seems unnecessary now, though not wrong. (It’s just weird
that it
frees that one, but not `s->used_clusters`...)
Hanna
