Messages in this thread Patch in this message | | | Date | Thu, 12 Oct 2023 16:04:02 +0800 | Subject | Re: [PATCH RFC] ubi: gluebi: Fix NULL pointer dereference caused by ftl notifier | From | ZhaoLong Wang <> |
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I'm very happy to receive a reply to the review.
> 2. fd = open(/dev/ubi0_0, O_WRONLY) > ubi_open_volume // vol->writers = 1 > > P1 P2 > gluebi_create -> mtd_device_register -> add_mtd_device: > device_register // dev/mtd1 is visible > > fd = open(/dev/mtd1, O_WRONLY) > gluebi_get_device > gluebi->desc = ubi_open_volume > gluebi->desc = ERR_PTR(EBUSY) > > ftl_add_mtd > mtd_read > gluebi_read > gluebi->desc is ERR_PTR (√)
The reproduction steps for situations 2 and 3 have been added to link[1]. Link: https://bugzilla.kernel.org/show_bug.cgi?id=217992 [1]
> 3. P1 P2 > gluebi_create -> mtd_device_register -> add_mtd_device: > device_register // dev/mtd1 is visible > > fd = open(/dev/mtd1, O_WRONLY) > gluebi_get_device > gluebi->desc = ubi_open_volume > > ftl_add_mtd > mtd_read > gluebi_read > gluebi->desc is not ERR_PTR/NULL > > close(fd) > gluebi_put_device > ubi_close_volume > kfree(desc) > ubi_read(gluebi->desc) // UAF (×) >
Yes, it's also a problem. Perhaps it should be set to NULL after destroying gluebi->desc.
> > No need to modify 'gluebi_write' and 'gluebi_erase'. >
The patch is as follows:
diff --git a/drivers/mtd/ubi/gluebi.c b/drivers/mtd/ubi/gluebi.c index 1b980d15d9fb..8fc6017d1155 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 isnt_get = unlikely(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 pointe dereference. + * Therefore, try to get the MTD device here. + */ + if (unlikely(isnt_get)) { + 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(isnt_get)) + __put_mtd_device(mtd); return err; }
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