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| author | Michal Privoznik <mprivozn@redhat.com> | 2014-06-25 10:38:41 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2014-06-26 15:53:52 +0200 |
| commit | a760715095e9cda6eb97486c040aa35f82297945 (patch) | |
| tree | 3394a38a63f59603179a44ced7dee6477ab5b912 /util | |
| parent | 20cca275c6190ca0027cf7dd369ba985e44a6537 (diff) | |
| download | qemu-a760715095e9cda6eb97486c040aa35f82297945.zip | |
qemu_opts_append: Play nicely with QemuOptsList's head
When running a libvirt test suite I've noticed the qemu-img is
crashing occasionally. Tracing the problem down led me to the
following valgrind output:
qemu.git $ valgrind -q ./qemu-img create -f qed -obacking_file=/dev/null,backing_fmt=raw qed
==14881== Invalid write of size 8
==14881== at 0x1D263F: qemu_opts_create (qemu-option.c:692)
==14881== by 0x130782: bdrv_img_create (block.c:5531)
==14881== by 0x118DE0: img_create (qemu-img.c:462)
==14881== by 0x11E7E4: main (qemu-img.c:2830)
==14881== Address 0x11fedd38 is 24 bytes inside a block of size 232 free'd
==14881== at 0x4C2CA5E: realloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==14881== by 0x592D35E: g_realloc (in /usr/lib64/libglib-2.0.so.0.3800.2)
==14881== by 0x1D38D8: qemu_opts_append (qemu-option.c:1129)
==14881== by 0x13075E: bdrv_img_create (block.c:5528)
==14881== by 0x118DE0: img_create (qemu-img.c:462)
==14881== by 0x11E7E4: main (qemu-img.c:2830)
==14881==
Formatting 'qed', fmt=qed size=0 backing_file='/dev/null' backing_fmt='raw' cluster_size=65536
==14881== Invalid write of size 8
==14881== at 0x1D28BE: qemu_opts_del (qemu-option.c:750)
==14881== by 0x130BF3: bdrv_img_create (block.c:5638)
==14881== by 0x118DE0: img_create (qemu-img.c:462)
==14881== by 0x11E7E4: main (qemu-img.c:2830)
==14881== Address 0x11fedd38 is 24 bytes inside a block of size 232 free'd
==14881== at 0x4C2CA5E: realloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==14881== by 0x592D35E: g_realloc (in /usr/lib64/libglib-2.0.so.0.3800.2)
==14881== by 0x1D38D8: qemu_opts_append (qemu-option.c:1129)
==14881== by 0x13075E: bdrv_img_create (block.c:5528)
==14881== by 0x118DE0: img_create (qemu-img.c:462)
==14881== by 0x11E7E4: main (qemu-img.c:2830)
==14881==
The problem is apparently in the qemu_opts_append(). Well, if it
gets called twice or more. On the first call, when @dst is NULL
some initialization is done during which @dst->head list gets
initialized. The list is initialized in a way, so that the list
tail points at the list head. However, the next time
qemu_opts_append() is called for new options to be added,
g_realloc() may move @dst to a new address making the old list tail
point at an invalid address. If that's the case, we must update the
list pointers.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'util')
| -rw-r--r-- | util/qemu-option.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/util/qemu-option.c b/util/qemu-option.c index 43de3add29..6dc27ce04f 100644 --- a/util/qemu-option.c +++ b/util/qemu-option.c @@ -1111,6 +1111,7 @@ QemuOptsList *qemu_opts_append(QemuOptsList *dst, size_t num_opts, num_dst_opts; QemuOptDesc *desc; bool need_init = false; + bool need_head_update; if (!list) { return dst; @@ -1121,6 +1122,12 @@ QemuOptsList *qemu_opts_append(QemuOptsList *dst, */ if (!dst) { need_init = true; + need_head_update = true; + } else { + /* Moreover, even if dst is not NULL, the realloc may move it to a + * different address in which case we may get a stale tail pointer + * in dst->head. */ + need_head_update = QTAILQ_EMPTY(&dst->head); } num_opts = count_opts_list(dst); @@ -1131,9 +1138,11 @@ QemuOptsList *qemu_opts_append(QemuOptsList *dst, if (need_init) { dst->name = NULL; dst->implied_opt_name = NULL; - QTAILQ_INIT(&dst->head); dst->merge_lists = false; } + if (need_head_update) { + QTAILQ_INIT(&dst->head); + } dst->desc[num_dst_opts].name = NULL; /* append list->desc to dst->desc */ |