[Qemu-devel] [PATCH] block/create: Do not abort if a block driver is not available

Philippe Mathieu-Daudé posted 1 patch 1 week ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20190911220849.30840-1-philmd@redhat.com
Maintainers: Max Reitz <mreitz@redhat.com>, Kevin Wolf <kwolf@redhat.com>
block/create.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

[Qemu-devel] [PATCH] block/create: Do not abort if a block driver is not available

Posted by Philippe Mathieu-Daudé 1 week ago
The 'blockdev-create' QMP command was introduced as experimental
feature in commit b0292b851b8, using the assert() debug call.
It got promoted to 'stable' command in 3fb588a0f2c, but the
assert call was not removed.

Some block drivers are optional, and bdrv_find_format() might
return a NULL value, triggering the assertion.

Stable code is not expected to abort, so return an error instead.

This is easily reproducible when libnfs is not installed:

  ./configure
  [...]
  module support    no
  Block whitelist (rw)
  Block whitelist (ro)
  libiscsi support  yes
  libnfs support    no
  [...]

Start QEMU:

  $ qemu-system-x86_64 -S -qmp unix:/tmp/qemu.qmp,server,nowait

Send the 'blockdev-create' with the 'nfs' driver:

  $ ( cat << 'EOF'
  {'execute': 'qmp_capabilities'}
  {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
  EOF
  ) | socat STDIO UNIX:/tmp/qemu.qmp
  {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 4}, "package": "v4.1.0-733-g89ea03a7dc"}, "capabilities": ["oob"]}}
  {"return": {}}

QEMU crashes:

  $ gdb qemu-system-x86_64 core
  Program received signal SIGSEGV, Segmentation fault.
  (gdb) bt
  #0  0x00007ffff510957f in raise () at /lib64/libc.so.6
  #1  0x00007ffff50f3895 in abort () at /lib64/libc.so.6
  #2  0x00007ffff50f3769 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
  #3  0x00007ffff5101a26 in .annobin_assert.c_end () at /lib64/libc.so.6
  #4  0x0000555555d7e1f1 in qmp_blockdev_create (job_id=0x555556baee40 "x", options=0x555557666610, errp=0x7fffffffc770) at block/create.c:69
  #5  0x0000555555c96b52 in qmp_marshal_blockdev_create (args=0x7fffdc003830, ret=0x7fffffffc7f8, errp=0x7fffffffc7f0) at qapi/qapi-commands-block-core.c:1314
  #6  0x0000555555deb0a0 in do_qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false, errp=0x7fffffffc898) at qapi/qmp-dispatch.c:131
  #7  0x0000555555deb2a1 in qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false) at qapi/qmp-dispatch.c:174

With this patch applied, QEMU returns a QMP error:

  {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
  {"id": "x", "error": {"class": "GenericError", "desc": "Block driver 'nfs' not found or not supported"}}

Reported-by: Xu Tian <xutian@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 block/create.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/block/create.c b/block/create.c
index 1bd00ed5f8..89812669df 100644
--- a/block/create.c
+++ b/block/create.c
@@ -64,9 +64,13 @@ void qmp_blockdev_create(const char *job_id, BlockdevCreateOptions *options,
     const char *fmt = BlockdevDriver_str(options->driver);
     BlockDriver *drv = bdrv_find_format(fmt);
 
+    if (!drv) {
+        error_setg(errp, "Block driver '%s' not found or not supported", fmt);
+        return;
+    }
+
     /* If the driver is in the schema, we know that it exists. But it may not
      * be whitelisted. */
-    assert(drv);
     if (bdrv_uses_whitelist() && !bdrv_is_whitelisted(drv, false)) {
         error_setg(errp, "Driver is not whitelisted");
         return;
-- 
2.20.1


Re: [Qemu-devel] [PATCH] block/create: Do not abort if a block driver is not available

Posted by Kevin Wolf 1 week ago
Am 12.09.2019 um 00:08 hat Philippe Mathieu-Daudé geschrieben:
> The 'blockdev-create' QMP command was introduced as experimental
> feature in commit b0292b851b8, using the assert() debug call.
> It got promoted to 'stable' command in 3fb588a0f2c, but the
> assert call was not removed.
> 
> Some block drivers are optional, and bdrv_find_format() might
> return a NULL value, triggering the assertion.
> 
> Stable code is not expected to abort, so return an error instead.
> 
> This is easily reproducible when libnfs is not installed:
> 
>   ./configure
>   [...]
>   module support    no
>   Block whitelist (rw)
>   Block whitelist (ro)
>   libiscsi support  yes
>   libnfs support    no
>   [...]
> 
> Start QEMU:
> 
>   $ qemu-system-x86_64 -S -qmp unix:/tmp/qemu.qmp,server,nowait
> 
> Send the 'blockdev-create' with the 'nfs' driver:
> 
>   $ ( cat << 'EOF'
>   {'execute': 'qmp_capabilities'}
>   {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
>   EOF
>   ) | socat STDIO UNIX:/tmp/qemu.qmp
>   {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 4}, "package": "v4.1.0-733-g89ea03a7dc"}, "capabilities": ["oob"]}}
>   {"return": {}}
> 
> QEMU crashes:
> 
>   $ gdb qemu-system-x86_64 core
>   Program received signal SIGSEGV, Segmentation fault.
>   (gdb) bt
>   #0  0x00007ffff510957f in raise () at /lib64/libc.so.6
>   #1  0x00007ffff50f3895 in abort () at /lib64/libc.so.6
>   #2  0x00007ffff50f3769 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
>   #3  0x00007ffff5101a26 in .annobin_assert.c_end () at /lib64/libc.so.6
>   #4  0x0000555555d7e1f1 in qmp_blockdev_create (job_id=0x555556baee40 "x", options=0x555557666610, errp=0x7fffffffc770) at block/create.c:69
>   #5  0x0000555555c96b52 in qmp_marshal_blockdev_create (args=0x7fffdc003830, ret=0x7fffffffc7f8, errp=0x7fffffffc7f0) at qapi/qapi-commands-block-core.c:1314
>   #6  0x0000555555deb0a0 in do_qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false, errp=0x7fffffffc898) at qapi/qmp-dispatch.c:131
>   #7  0x0000555555deb2a1 in qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false) at qapi/qmp-dispatch.c:174
> 
> With this patch applied, QEMU returns a QMP error:
> 
>   {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
>   {"id": "x", "error": {"class": "GenericError", "desc": "Block driver 'nfs' not found or not supported"}}
> 
> Reported-by: Xu Tian <xutian@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Thanks, applied to the block branch.

Kevin

Re: [Qemu-devel] [Qemu-block] [PATCH] block/create: Do not abort if a block driver is not available

Posted by John Snow 1 week ago

On 9/11/19 6:08 PM, Philippe Mathieu-Daudé wrote:
> The 'blockdev-create' QMP command was introduced as experimental
> feature in commit b0292b851b8, using the assert() debug call.
> It got promoted to 'stable' command in 3fb588a0f2c, but the
> assert call was not removed.
> 
> Some block drivers are optional, and bdrv_find_format() might
> return a NULL value, triggering the assertion.
> 
> Stable code is not expected to abort, so return an error instead.
> 
> This is easily reproducible when libnfs is not installed:
> 
>   ./configure
>   [...]
>   module support    no
>   Block whitelist (rw)
>   Block whitelist (ro)
>   libiscsi support  yes
>   libnfs support    no
>   [...]
> 
> Start QEMU:
> 
>   $ qemu-system-x86_64 -S -qmp unix:/tmp/qemu.qmp,server,nowait
> 
> Send the 'blockdev-create' with the 'nfs' driver:
> 
>   $ ( cat << 'EOF'
>   {'execute': 'qmp_capabilities'}
>   {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
>   EOF
>   ) | socat STDIO UNIX:/tmp/qemu.qmp
>   {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 4}, "package": "v4.1.0-733-g89ea03a7dc"}, "capabilities": ["oob"]}}
>   {"return": {}}
> 
> QEMU crashes:
> 
>   $ gdb qemu-system-x86_64 core
>   Program received signal SIGSEGV, Segmentation fault.
>   (gdb) bt
>   #0  0x00007ffff510957f in raise () at /lib64/libc.so.6
>   #1  0x00007ffff50f3895 in abort () at /lib64/libc.so.6
>   #2  0x00007ffff50f3769 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
>   #3  0x00007ffff5101a26 in .annobin_assert.c_end () at /lib64/libc.so.6
>   #4  0x0000555555d7e1f1 in qmp_blockdev_create (job_id=0x555556baee40 "x", options=0x555557666610, errp=0x7fffffffc770) at block/create.c:69
>   #5  0x0000555555c96b52 in qmp_marshal_blockdev_create (args=0x7fffdc003830, ret=0x7fffffffc7f8, errp=0x7fffffffc7f0) at qapi/qapi-commands-block-core.c:1314
>   #6  0x0000555555deb0a0 in do_qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false, errp=0x7fffffffc898) at qapi/qmp-dispatch.c:131
>   #7  0x0000555555deb2a1 in qmp_dispatch (cmds=0x55555645de70 <qmp_commands>, request=0x7fffdc005c70, allow_oob=false) at qapi/qmp-dispatch.c:174
> 
> With this patch applied, QEMU returns a QMP error:
> 
>   {'execute': 'blockdev-create', 'arguments': {'job-id': 'x', 'options': {'size': 0, 'driver': 'nfs', 'location': {'path': '/', 'server': {'host': '::1', 'type': 'inet'}}}}, 'id': 'x'}
>   {"id": "x", "error": {"class": "GenericError", "desc": "Block driver 'nfs' not found or not supported"}}
> 
> Reported-by: Xu Tian <xutian@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Reviewed-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [PATCH] block/create: Do not abort if a block driver is not available

Posted by Eric Blake 1 week ago
On 9/11/19 5:08 PM, Philippe Mathieu-Daudé wrote:
> The 'blockdev-create' QMP command was introduced as experimental
> feature in commit b0292b851b8, using the assert() debug call.
> It got promoted to 'stable' command in 3fb588a0f2c, but the
> assert call was not removed.
> 
> Some block drivers are optional, and bdrv_find_format() might
> return a NULL value, triggering the assertion.
> 
> Stable code is not expected to abort, so return an error instead.
> 

> 
> Reported-by: Xu Tian <xutian@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  block/create.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/block/create.c b/block/create.c
> index 1bd00ed5f8..89812669df 100644
> --- a/block/create.c
> +++ b/block/create.c
> @@ -64,9 +64,13 @@ void qmp_blockdev_create(const char *job_id, BlockdevCreateOptions *options,
>      const char *fmt = BlockdevDriver_str(options->driver);
>      BlockDriver *drv = bdrv_find_format(fmt);
>  
> +    if (!drv) {
> +        error_setg(errp, "Block driver '%s' not found or not supported", fmt);
> +        return;
> +    }
> +
>      /* If the driver is in the schema, we know that it exists. But it may not
>       * be whitelisted. */
> -    assert(drv);
>      if (bdrv_uses_whitelist() && !bdrv_is_whitelisted(drv, false)) {
>          error_setg(errp, "Driver is not whitelisted");

Matches that we error for not being on the whitelist.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org