- Rewrite
quota->memory + memory > U32_MAX
as
U32_MAX - quota->memory < memory
There is no overflow issue in the original expression on 32-bit
because the previous one (available - quota->memory < memory)
guarantees that quota->memory + memory doesn't exceed `available'
which is <= U32_MAX in that case. But lets replace it with less
ambiguous variant.
- Replace
quota->fds + fds < quota->fds ||
quota->fds + fds > KDBUS_CONN_MAX_FDS_PER_USER
with
quota->fds > KDBUS_CONN_MAX_FDS_PER_USER ||
KDBUS_CONN_MAX_FDS_PER_USER - quota->fds < fds
Reading the code, one can assume that the first original expression
is there to ensure that quota->fds won't overflow after
quota->fds += fds, but what it really does is testing for
size_t overflow in `quota->fds + fds' to be safe in the second
expression (as fds is size_t, quota->fds is converted to bigger
type).
Rewrite it in more obvious way. KDBUS_CONN_MAX_FDS_PER_USER is
checked at compile time to fill in quota->fds type (there is
BUILD_BUG_ON), so no further checks for quota->fds overflow are
needed.
Signed-off-by: Sergei Zviagintsev <ser...@s15v.net>
---
ipc/kdbus/connection.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/ipc/kdbus/connection.c b/ipc/kdbus/connection.c
index c57ff2c846ee..b32b4f981618 100644
--- a/ipc/kdbus/connection.c
+++ b/ipc/kdbus/connection.c
@@ -717,12 +717,12 @@ int kdbus_conn_quota_inc(struct kdbus_conn *c, struct
kdbus_user *u,
if (available < quota->memory ||
available - quota->memory < memory ||
- quota->memory + memory > U32_MAX)
+ U32_MAX - quota->memory < memory)
return -ENOBUFS;
if (quota->msgs >= KDBUS_CONN_MAX_MSGS)
return -ENOBUFS;
- if (quota->fds + fds < quota->fds ||
- quota->fds + fds > KDBUS_CONN_MAX_FDS_PER_USER)
+ if (quota->fds > KDBUS_CONN_MAX_FDS_PER_USER ||
+ KDBUS_CONN_MAX_FDS_PER_USER - quota->fds < fds)
return -EMFILE;
quota->memory += memory;
--
1.8.3.1
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