linux-kernel - [PATCH] stat: don't fail if the major number is >= 256

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Date:   Mon, 11 Apr 2022 10:43:33 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] stat: don't fail if the major number is >= 256

If you run a program compiled with OpenWatcom for Linux on a filesystem on 
NVMe, all "stat" syscalls fail with -EOVERFLOW. The reason is that the 
NVMe driver allocates a device with the major number 259 and it doesn't 
pass the "old_valid_dev" test.

This patch removes the tests - it's better to wrap around than to return
an error. (note that cp_old_stat also doesn't report an error and wraps
the number around)

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

---
 fs/stat.c |    6 ------
 1 file changed, 6 deletions(-)

Index: linux-5.17.2/fs/stat.c
===================================================================
--- linux-5.17.2.orig/fs/stat.c	2022-04-10 21:39:27.000000000 +0200
+++ linux-5.17.2/fs/stat.c	2022-04-10 21:42:43.000000000 +0200
@@ -334,7 +334,6 @@ SYSCALL_DEFINE2(fstat, unsigned int, fd,
 #  define choose_32_64(a,b) b
 #endif
 
-#define valid_dev(x)  choose_32_64(old_valid_dev(x),true)
 #define encode_dev(x) choose_32_64(old_encode_dev,new_encode_dev)(x)
 
 #ifndef INIT_STRUCT_STAT_PADDING
@@ -345,8 +344,6 @@ static int cp_new_stat(struct kstat *sta
 {
 	struct stat tmp;
 
-	if (!valid_dev(stat->dev) || !valid_dev(stat->rdev))
-		return -EOVERFLOW;
 #if BITS_PER_LONG == 32
 	if (stat->size > MAX_NON_LFS)
 		return -EOVERFLOW;
@@ -644,9 +641,6 @@ static int cp_compat_stat(struct kstat *
 {
 	struct compat_stat tmp;
 
-	if (!old_valid_dev(stat->dev) || !old_valid_dev(stat->rdev))
-		return -EOVERFLOW;
-
 	memset(&tmp, 0, sizeof(tmp));
 	tmp.st_dev = old_encode_dev(stat->dev);
 	tmp.st_ino = stat->ino;