65 lines
2.7 KiB
Diff
65 lines
2.7 KiB
Diff
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From 93e7987cb5a7b33c2d2e0a02b7f310955ca11851 Mon Sep 17 00:00:00 2001
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From: Christian Schoenebeck <qemu_oss@crudebyte.com>
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Date: Tue, 5 Nov 2024 11:25:26 +0100
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Subject: [PATCH] 9pfs: fix crash on 'Treaddir' request
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A bad (broken or malicious) 9p client (guest) could cause QEMU host to
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crash by sending a 9p 'Treaddir' request with a numeric file ID (FID) that
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was previously opened for a file instead of an expected directory:
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#0 0x0000762aff8f4919 in __GI___rewinddir (dirp=0xf) at
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../sysdeps/unix/sysv/linux/rewinddir.c:29
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#1 0x0000557b7625fb40 in do_readdir_many (pdu=0x557bb67d2eb0,
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fidp=0x557bb67955b0, entries=0x762afe9fff58, offset=0, maxsize=131072,
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dostat=<optimized out>) at ../hw/9pfs/codir.c:101
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#2 v9fs_co_readdir_many (pdu=pdu@entry=0x557bb67d2eb0,
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fidp=fidp@entry=0x557bb67955b0, entries=entries@entry=0x762afe9fff58,
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offset=0, maxsize=131072, dostat=false) at ../hw/9pfs/codir.c:226
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#3 0x0000557b7625c1f9 in v9fs_do_readdir (pdu=0x557bb67d2eb0,
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fidp=0x557bb67955b0, offset=<optimized out>,
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max_count=<optimized out>) at ../hw/9pfs/9p.c:2488
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#4 v9fs_readdir (opaque=0x557bb67d2eb0) at ../hw/9pfs/9p.c:2602
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That's because V9fsFidOpenState was declared as union type. So the
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same memory region is used for either an open POSIX file handle (int),
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or a POSIX DIR* pointer, etc., so 9p server incorrectly used the
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previously opened (valid) POSIX file handle (0xf) as DIR* pointer,
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eventually causing a crash in glibc's rewinddir() function.
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Root cause was therefore a missing check in 9p server's 'Treaddir'
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request handler, which must ensure that the client supplied FID was
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really opened as directory stream before trying to access the
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aforementioned union and its DIR* member.
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Cc: qemu-stable@nongnu.org
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Fixes: d62dbb51f7 ("virtio-9p: Add fidtype so that we can do type ...")
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Reported-by: Akihiro Suda <suda.kyoto@gmail.com>
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Tested-by: Akihiro Suda <suda.kyoto@gmail.com>
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Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
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Reviewed-by: Greg Kurz <groug@kaod.org>
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Message-Id: <E1t8GnN-002RS8-E2@kylie.crudebyte.com>
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Signed-off-by: Zhongrui Tang <tangzhongrui_yewu@cmss.chinamobile.com>
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---
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hw/9pfs/9p.c | 5 +++++
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1 file changed, 5 insertions(+)
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diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
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index af636cfb2d..9a291d1b51 100644
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--- a/hw/9pfs/9p.c
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+++ b/hw/9pfs/9p.c
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@@ -2587,6 +2587,11 @@ static void coroutine_fn v9fs_readdir(void *opaque)
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retval = -EINVAL;
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goto out_nofid;
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}
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+ if (fidp->fid_type != P9_FID_DIR) {
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+ warn_report_once("9p: bad client: T_readdir on non-directory stream");
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+ retval = -ENOTDIR;
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+ goto out;
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+ }
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if (!fidp->fs.dir.stream) {
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retval = -EINVAL;
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goto out;
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--
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2.41.0.windows.1
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