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SubjectRe: [PATCH v2 13/19] udf: prevent bounds-check bypass via speculative execution
On Thu 11-01-18 16:47:35, Dan Williams wrote:
> Static analysis reports that 'eahd->appAttrLocation' and
> 'eahd->impAttrLocation' may be a user controlled values that are used as
> data dependencies for calculating source and destination buffers for
> memmove operations. In order to avoid potential leaks of kernel memory
> values, block speculative execution of the instruction stream that could
> issue further reads based on invalid 'aal' or 'ial' values.
>
> Based on an original patch by Elena Reshetova.
>
> Cc: Jan Kara <jack@suse.com>
> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Dan, I've already emailed to you [1] why I don't think this patch is needed
at all. Do you disagree or did my email just get lost?

[1] https://marc.info/?l=linux-arch&m=151540683024125&w=2

Honza

> ---
> fs/udf/misc.c | 40 ++++++++++++++++++++++------------------
> 1 file changed, 22 insertions(+), 18 deletions(-)
>
> diff --git a/fs/udf/misc.c b/fs/udf/misc.c
> index 401e64cde1be..693e24699928 100644
> --- a/fs/udf/misc.c
> +++ b/fs/udf/misc.c
> @@ -22,6 +22,7 @@
> #include "udfdecl.h"
>
> #include <linux/fs.h>
> +#include <linux/nospec.h>
> #include <linux/string.h>
> #include <linux/crc-itu-t.h>
>
> @@ -51,6 +52,8 @@ struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
> int offset;
> uint16_t crclen;
> struct udf_inode_info *iinfo = UDF_I(inode);
> + uint8_t *ea_dst, *ea_src;
> + uint32_t aal, ial;
>
> ea = iinfo->i_ext.i_data;
> if (iinfo->i_lenEAttr) {
> @@ -100,33 +103,34 @@ struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
>
> offset = iinfo->i_lenEAttr;
> if (type < 2048) {
> - if (le32_to_cpu(eahd->appAttrLocation) <
> - iinfo->i_lenEAttr) {
> - uint32_t aal =
> - le32_to_cpu(eahd->appAttrLocation);
> - memmove(&ea[offset - aal + size],
> - &ea[aal], offset - aal);
> + aal = le32_to_cpu(eahd->appAttrLocation);
> + ea_dst = array_ptr(ea, offset - aal + size,
> + iinfo->i_lenEAttr);
> + ea_src = array_ptr(ea, aal, iinfo->i_lenEAttr);
> + if (ea_dst && ea_src) {
> + memmove(ea_dst, ea_src, offset - aal);
> offset -= aal;
> eahd->appAttrLocation =
> cpu_to_le32(aal + size);
> }
> - if (le32_to_cpu(eahd->impAttrLocation) <
> - iinfo->i_lenEAttr) {
> - uint32_t ial =
> - le32_to_cpu(eahd->impAttrLocation);
> - memmove(&ea[offset - ial + size],
> - &ea[ial], offset - ial);
> +
> + ial = le32_to_cpu(eahd->impAttrLocation);
> + ea_dst = array_ptr(ea, offset - ial + size,
> + iinfo->i_lenEAttr);
> + ea_src = array_ptr(ea, ial, iinfo->i_lenEAttr);
> + if (ea_dst && ea_src) {
> + memmove(ea_dst, ea_src, offset - ial);
> offset -= ial;
> eahd->impAttrLocation =
> cpu_to_le32(ial + size);
> }
> } else if (type < 65536) {
> - if (le32_to_cpu(eahd->appAttrLocation) <
> - iinfo->i_lenEAttr) {
> - uint32_t aal =
> - le32_to_cpu(eahd->appAttrLocation);
> - memmove(&ea[offset - aal + size],
> - &ea[aal], offset - aal);
> + aal = le32_to_cpu(eahd->appAttrLocation);
> + ea_dst = array_ptr(ea, offset - aal + size,
> + iinfo->i_lenEAttr);
> + ea_src = array_ptr(ea, aal, iinfo->i_lenEAttr);
> + if (ea_dst && ea_src) {
> + memmove(ea_dst, ea_src, offset - aal);
> offset -= aal;
> eahd->appAttrLocation =
> cpu_to_le32(aal + size);
>
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR

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