On 6/24/20 3:53 AM, Bodo Stroesser wrote: > 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 maximum 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://urldefense.com/v3/__https://bugzilla.kernel.org/show_bug.cgi?id=208045*c10__;Iw!!GqivPVa7Brio!Kxr99oE0H1b9Ily4SE23nDN7ElSf8Tclo1RILfNSXb6iPh6DA5cSgtBQQsLMBKdrLsmT$ > > Signed-off-by: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx> > Tested-by: JiangYu <lnsyyj@xxxxxxxxxxx> > --- > 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 3885ca532f8f..82e476d48194 100644 > --- a/drivers/target/target_core_user.c > +++ b/drivers/target/target_core_user.c > @@ -1221,7 +1221,14 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev) > > struct tcmu_cmd_entry *entry = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned; > > - 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, > Thanks again. Acked-by: Mike Christie <michael.christie@xxxxxxxxxx>
