cygwin: pread/pwrite: prevent EBADF error after fork()

If the parent process has already used pread() or pwrite(), these functions fail with EBADF if used on the inherited fd. Ensure that fix_after_fork() is called to invalidate the prw_handle. This issue has been detected by 'stress-ng --pseek 1'. Fixes: c36cd56 ("* fhandler.cc (fhandler_base::open): Drop local create_options variable.") Signed-off-by: Christian Franke <[email protected]>
jonathanlyonmoore · Oct 23, 2024 · bdd06f8 · bdd06f8
1 parent 1b7c72f
commit bdd06f8
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diff --git a/winsup/cygwin/fhandler/disk_file.cc b/winsup/cygwin/fhandler/disk_file.cc
@@ -1803,6 +1803,9 @@ fhandler_disk_file::prw_open (bool write, void *aio)
       return -1;
     }
 
+  /* prw_handle is invalid after fork. */
+  need_fork_fixup (true);
+
   /* record prw_handle's asyncness for subsequent pread/pwrite operations */
   prw_handle_isasync = !!aio;
   return 0;

diff --git a/winsup/cygwin/release/3.5.5 b/winsup/cygwin/release/3.5.5
@@ -7,3 +7,6 @@ Fixes:
 
 - Fix a regression in 3.5.4 that writing to pipe extremely slows down.
   Addresses: https://cygwin.com/pipermail/cygwin/2024-August/256398.html
+
+- Fix pread() and pwrite() EBADF error after fork().
+  Addresses: https://sourceware.org/pipermail/cygwin/2024-September/256468.html