Patch "Input: ff-core - prefer struct_size over open coded arithmetic" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    Input: ff-core - prefer struct_size over open coded arithmetic

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     input-ff-core-prefer-struct_size-over-open-coded-ari.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fa8197276f1fa560aae88bb343d1e93205cba24d
Author: Erick Archer <erick.archer@xxxxxxxxxxx>
Date:   Sat Apr 27 17:05:56 2024 +0200

    Input: ff-core - prefer struct_size over open coded arithmetic
    
    [ Upstream commit a08b8f8557ad88ffdff8905e5da972afe52e3307 ]
    
    This is an effort to get rid of all multiplications from allocation
    functions in order to prevent integer overflows [1][2].
    
    As the "ff" variable is a pointer to "struct ff_device" and this
    structure ends in a flexible array:
    
    struct ff_device {
            [...]
            struct file *effect_owners[] __counted_by(max_effects);
    };
    
    the preferred way in the kernel is to use the struct_size() helper to
    do the arithmetic instead of the calculation "size + count * size" in
    the kzalloc() function.
    
    The struct_size() helper returns SIZE_MAX on overflow. So, refactor
    the comparison to take advantage of this.
    
    This way, the code is more readable and safer.
    
    This code was detected with the help of Coccinelle, and audited and
    modified manually.
    
    Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
    Link: https://github.com/KSPP/linux/issues/160 [2]
    Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
    Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/AS8PR02MB72371E646714BAE2E51A6A378B152@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/input/ff-core.c b/drivers/input/ff-core.c
index 66a46c84e28f5..7d83de2c536dd 100644
--- a/drivers/input/ff-core.c
+++ b/drivers/input/ff-core.c
@@ -24,8 +24,10 @@
 /* #define DEBUG */
 
 #include <linux/input.h>
+#include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/overflow.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 
@@ -330,9 +332,8 @@ int input_ff_create(struct input_dev *dev, unsigned int max_effects)
 		return -EINVAL;
 	}
 
-	ff_dev_size = sizeof(struct ff_device) +
-				max_effects * sizeof(struct file *);
-	if (ff_dev_size < max_effects) /* overflow */
+	ff_dev_size = struct_size(ff, effect_owners, max_effects);
+	if (ff_dev_size == SIZE_MAX) /* overflow */
 		return -EINVAL;
 
 	ff = kzalloc(ff_dev_size, GFP_KERNEL);