Re: [PATCH] hw/9pfs: Follow native symlinks when security-model=mapped

[Andrey Erokhin]

On 21/11/2025 17:20, Christian Schoenebeck wrote:

Andrey, just some minor issues from my side below:

Git commit log message should not exceed 76 characters per line.

TBH, I'm not used to sending patches by git, it was just an e-mail message, not 
a commit message

QEMU issues:
https://gitlab.com/qemu-project/qemu/-/issues/173 (from
https://bugs.launchpad.net/qemu/+bug/1831354)
https://gitlab.com/qemu-project/qemu/-/issues/3088 (dup of the first one)

This should be:

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/173

Fixed in the attached patch. Or should I start a new [PATCH v2] thread?

The other links can be dropped. They are already linked by #173.

Signed-off-by: Andrey Erokhin <language.law...@gmail.com>


diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 31e216227c..b4f8be2c81 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -468,12 +468,14 @@ static ssize_t local_readlink(FsContext *fs_ctx,
V9fsPath *fs_path,

           fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0);
           if (fd == -1) {
+            if (errno == ELOOP) goto native_symlink;
               return -1;
           }

scripts/checkpatch.pl complaints:

ERROR: trailing statements should be on next line
#33: FILE: hw/9pfs/9p-local.c:471:
+            if (errno == ELOOP) goto native_symlink;

ERROR: braces {} are necessary for all arms of this statement
#33: FILE: hw/9pfs/9p-local.c:471:
+            if (errno == ELOOP) goto native_symlink;
[...]

Fixed

           tsize = RETRY_ON_EINTR(read(fd, (void *)buf, bufsz));
           close_preserve_errno(fd);
       } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
                  (fs_ctx->export_flags & V9FS_SM_NONE)) {
+native_symlink:;

Semicolon is unnecessary here, isn't it?

https://port70.net/~nsz/c/c11/n1570.html#6.8.1 Labeled statements:

labeled-statement:
        identifier : statement

Can't be a declaration
hw/9pfs: follow native symlinks in security-model=mapped

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/173

Signed-off-by: Andrey Erokhin <language.law...@gmail.com>
---
 hw/9pfs/9p-local.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 31e216227c..5ce97b76a6 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -468,12 +468,16 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path,
 
         fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0);
         if (fd == -1) {
+            if (errno == ELOOP) {
+                goto native_symlink;
+            }
             return -1;
         }
         tsize = RETRY_ON_EINTR(read(fd, (void *)buf, bufsz));
         close_preserve_errno(fd);
     } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
                (fs_ctx->export_flags & V9FS_SM_NONE)) {
+    native_symlink:;
         char *dirpath = g_path_get_dirname(fs_path->data);
         char *name = g_path_get_basename(fs_path->data);
         int dirfd;
-- 
2.34.1