[newlib-cygwin/main] Cygwin: fallocate(2): fix offset and length sanity check

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7f88c8e0b316e7832e58ff878cffb62460b2902f

commit 7f88c8e0b316e7832e58ff878cffb62460b2902f
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Tue Dec 5 22:08:42 2023 +0100
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Tue Dec 5 22:20:42 2023 +0100

    Cygwin: fallocate(2): fix offset and length sanity check
    
    - len must not be <= 0
    - offset + len must not exceed off_t (max. file size)
    
    Fixes: e01c50c7b0a6 ("Cygwin: introduce fallocate(2)")
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/syscalls.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 3edb55bc608f..b6aeb47c86a4 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -3005,8 +3005,10 @@ fallocate (int fd, int mode, off_t offset, off_t len)
   else if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE))
 	   == FALLOC_FL_PUNCH_HOLE)
     res = EOPNOTSUPP;
-  else if (offset < 0 || len == 0)
+  else if (offset < 0 || len <= 0)
     res = EINVAL;
+  else if (INT64_MAX - len < offset)
+    res = EFBIG;
   else
     {
       cygheap_fdget cfd (fd);