hostdisk: fix device detection

Condition was apparently reversed so GRUB assumed all devices were
files. This later made it skip BLKFLSBUF ioctl on Linux which caused
various page cache coherency issues. Observed were

- failure to validate blocklist install (read content did not match
  just written)

- failure to detect Linux MD on disk after online hot addition
  (GRUB got stale superblock)

Closes: 46691

diff --git a/grub-core/kern/emu/hostdisk.c b/grub-core/kern/emu/hostdisk.c
index 610518d0ca74d94ff4c0e2e5322630c5c739df87..87e3e251204f90348a45ea9079c716e052b5106b 100644 (file)
--- a/grub-core/kern/emu/hostdisk.c
+++ b/grub-core/kern/emu/hostdisk.c
@@ -161,9 +161,9 @@ grub_util_biosdisk_open (const char *name, grub_disk_t disk)
     {
       struct stat st;
 # if GRUB_DISK_DEVS_ARE_CHAR
-      if (fstat (fd, &st) < 0 || ! S_ISCHR (st.st_mode))
+      if (fstat (fd, &st) >= 0 && S_ISCHR (st.st_mode))
 # else
-      if (fstat (fd, &st) < 0 || ! S_ISBLK (st.st_mode))
+      if (fstat (fd, &st) >= 0 && S_ISBLK (st.st_mode))
 # endif
        data->is_disk = 1;
     }