[xen master] xen/common: llc-coloring: Fix off-by-one in parse_color_config()

[patchbot@xxxxxxx]

commit dc28f531e6a29a6fdd58f24073dfb48af06b8334
Author:     Michal Orzel <michal.orzel@xxxxxxx>
AuthorDate: Fri Apr 10 10:29:55 2026 +0200
Commit:     Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Fri Apr 10 12:14:05 2026 +0200

    xen/common: llc-coloring: Fix off-by-one in parse_color_config()
    
    The check uses (*num_colors + (end - start + 1)) >= max_num_colors, which
    rejects a configuration where exactly max_num_colors colors are specified.
    For example, if max_num_colors is 4 and *num_colors is 0, a range "0-3"
    gives (end - start + 1) = 4, and (0 + 4) >= 4 is true, incorrectly
    returning -EINVAL.
    
    Fix this by switching the overflow condition to the state before commit
    cba8a584de17 that regressed the behavior (i.e. don't add 1).
    
    Fixes: cba8a584de17 ("llc-coloring: improve checking while parsing")
    Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
    Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
 xen/common/llc-coloring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/llc-coloring.c b/xen/common/llc-coloring.c
index eb7c72b240..6dc614739a 100644
--- a/xen/common/llc-coloring.c
+++ b/xen/common/llc-coloring.c
@@ -78,7 +78,7 @@ static int __init parse_color_config(const char *buf, 
unsigned int colors[],
 
         if ( end >= NR_LLC_COLORS || start > end ||
              (end - start) >= (UINT_MAX - *num_colors) ||
-             (*num_colors + (end - start + 1)) >= max_num_colors )
+             (*num_colors + (end - start)) >= max_num_colors )
             return -EINVAL;
 
         /* Colors are range checked in check_colors() */
--
generated by git-patchbot for /home/xen/git/xen.git#master