idr: Fix integer overflow in idr_for_each_entry

BugLink: https://bugs.launchpad.net/bugs/1855787
[ Upstream commit f6341c5af4e6e15041be39976d16deca789555fa ]

If there is an entry at INT_MAX then idr_for_each_entry() will increment
id after handling it.  This is undefined behaviour, and is caught by
UBSAN.  Adding 1U to id forces the operation to be carried out as an
unsigned addition which (when assigned to id) will result in INT_MIN.
Since there is never an entry stored at INT_MIN, idr_get_next() will
return NULL, ending the loop as expected.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/include/linux/idr.h b/include/linux/idr.h
index fa14f834e4ede3a81e7e6182c889fec338b2495f..51adb0b8dbc74234f8497b6a369a93665d3c5b47 100644 (file)
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -206,7 +206,7 @@ static inline void *idr_find(const struct idr *idr, int id)
  * is convenient for a "not found" value.
  */
 #define idr_for_each_entry(idr, entry, id)                     \
-       for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)
+       for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; id += 1U)
 #define idr_for_each_entry_ext(idr, entry, id)                 \
        for (id = 0; ((entry) = idr_get_next_ext(idr, &(id))) != NULL; ++id)