Messages in this thread | | | Subject | Re: [PATCH v2] ubi: gluebi: Fix NULL pointer dereference caused by ftl notifier | From | Zhihao Cheng <> | Date | Thu, 19 Oct 2023 09:57:18 +0800 |
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在 2023/10/18 20:16, ZhaoLong Wang 写道: > If both flt.ko and gluebi.ko are loaded, the notiier of ftl > triggers NULL pointer dereference when trying to access > ‘gluebi->desc’ in gluebi_read(). > > ubi_gluebi_init > ubi_register_volume_notifier > ubi_enumerate_volumes > ubi_notify_all > gluebi_notify nb->notifier_call() > gluebi_create > mtd_device_register > mtd_device_parse_register > add_mtd_device > blktrans_notify_add not->add() > ftl_add_mtd tr->add_mtd() > scan_header > mtd_read > mtd_read > mtd_read_oob > gluebi_read mtd->read() > gluebi->desc - NULL > > Detailed reproduction information available at the link[1], > > In the normal case, obtain gluebi->desc in the gluebi_get_device(), > and accesses gluebi->desc in the gluebi_read(). However, > gluebi_get_device() is not executed in advance in the > ftl_add_mtd() process, which leads to NULL pointer dereference. > > The value of gluebi->desc may also be a negative error code, which > triggers the page fault error. > > This patch has the following modifications: > > 1. Do not assign gluebi->desc to the error code. Use the NULL instead. > > 2. Always check the validity of gluebi->desc in gluebi_read() If the > gluebi->desc is NULL, try to get MTD device. > > Such a modification currently works because the mutex "mtd_table_mutex" > is held on all necessary paths, including the ftl_add_mtd() call path, > open and close paths. Therefore, many race condition can be avoided. > > Fixes: 2ba3d76a1e29 ("UBI: make gluebi a separate module") > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217992 [1] > Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com> > --- > drivers/mtd/ubi/gluebi.c | 37 +++++++++++++++++++++++++++++++------ > 1 file changed, 31 insertions(+), 6 deletions(-) >
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
> diff --git a/drivers/mtd/ubi/gluebi.c b/drivers/mtd/ubi/gluebi.c > index 1b980d15d9fb..0ca7f104adbf 100644 > --- a/drivers/mtd/ubi/gluebi.c > +++ b/drivers/mtd/ubi/gluebi.c > @@ -85,6 +85,7 @@ static int gluebi_get_device(struct mtd_info *mtd) > { > struct gluebi_device *gluebi; > int ubi_mode = UBI_READONLY; > + struct ubi_volume_desc *vdesc; > > if (mtd->flags & MTD_WRITEABLE) > ubi_mode = UBI_READWRITE; > @@ -109,12 +110,14 @@ static int gluebi_get_device(struct mtd_info *mtd) > * This is the first reference to this UBI volume via the MTD device > * interface. Open the corresponding volume in read-write mode. > */ > - gluebi->desc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id, > + vdesc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id, > ubi_mode); > - if (IS_ERR(gluebi->desc)) { > + if (IS_ERR(vdesc)) { > + gluebi->desc = NULL; > mutex_unlock(&devices_mutex); > - return PTR_ERR(gluebi->desc); > + return PTR_ERR(vdesc); > } > + gluebi->desc = vdesc; > gluebi->refcnt += 1; > mutex_unlock(&devices_mutex); > return 0; > @@ -134,8 +137,10 @@ static void gluebi_put_device(struct mtd_info *mtd) > gluebi = container_of(mtd, struct gluebi_device, mtd); > mutex_lock(&devices_mutex); > gluebi->refcnt -= 1; > - if (gluebi->refcnt == 0) > + if (gluebi->refcnt == 0) { > ubi_close_volume(gluebi->desc); > + gluebi->desc = NULL; > + } > mutex_unlock(&devices_mutex); > } > > @@ -154,9 +159,26 @@ static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len, > size_t *retlen, unsigned char *buf) > { > int err = 0, lnum, offs, bytes_left; > - struct gluebi_device *gluebi; > + struct gluebi_device *gluebi = container_of(mtd, struct gluebi_device, > + mtd); > + int no_desc = gluebi->desc == NULL ? 1 : 0; > + > + /** > + * In normal case, the UBI volume desc has been initialized by > + * ->_get_device(). However, in the ftl notifier process, the > + * ->_get_device() is not executed in advance and the MTD device > + * is directly scanned which cause NULL pointer dereference. > + * Therefore, try to get the MTD device here. > + */ > + if (unlikely(no_desc)) { > + err = __get_mtd_device(mtd); > + if (err) { > + err_msg("cannot get MTD device %d, UBI device %d, volume %d, error %d", > + mtd->index, gluebi->ubi_num, gluebi->vol_id, err); > + return err; > + } > + } > > - gluebi = container_of(mtd, struct gluebi_device, mtd); > lnum = div_u64_rem(from, mtd->erasesize, &offs); > bytes_left = len; > while (bytes_left) { > @@ -176,6 +198,9 @@ static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len, > } > > *retlen = len - bytes_left; > + > + if (unlikely(no_desc)) > + __put_mtd_device(mtd); > return err; > } > >
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