From: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx> [ Upstream commit 5a0c256d96f020e4771f6fd5524b80f89a2d3132 ] If tcmu_handle_completions() has to process a padding shorter than sizeof(struct tcmu_cmd_entry), the current call to tcmu_flush_dcache_range() with sizeof(struct tcmu_cmd_entry) as length param is wrong and causes crashes on e.g. ARM, because tcmu_flush_dcache_range() in this case calls flush_dcache_page(vmalloc_to_page(start)); with start being an invalid address above the end of the vmalloc'ed area. The fix is to use the minimum of remaining ring space and sizeof(struct tcmu_cmd_entry) as the length param. The patch was tested on kernel 4.19.118. See https://bugzilla.kernel.org/show_bug.cgi?id=208045#c10 Link: https://lore.kernel.org/r/20200629093756.8947-1-bstroesser@xxxxxxxxxxxxxx Tested-by: JiangYu <lnsyyj@xxxxxxxxxxx> Acked-by: Mike Christie <michael.christie@xxxxxxxxxx> Signed-off-by: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/target/target_core_user.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 1a83456a65a00..693fbb2858404 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -666,7 +666,14 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev) struct tcmu_cmd_entry *entry = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned; struct tcmu_cmd *cmd; - tcmu_flush_dcache_range(entry, sizeof(*entry)); + /* + * Flush max. up to end of cmd ring since current entry might + * be a padding that is shorter than sizeof(*entry) + */ + size_t ring_left = head_to_end(udev->cmdr_last_cleaned, + udev->cmdr_size); + tcmu_flush_dcache_range(entry, ring_left < sizeof(*entry) ? + ring_left : sizeof(*entry)); if (tcmu_hdr_get_op(entry->hdr.len_op) == TCMU_OP_PAD) { UPDATE_HEAD(udev->cmdr_last_cleaned, -- 2.25.1
