Re: [PATCH 0/2] apparmor unaligned memory fixes

John Paul Adrian Glaubitz
2025-11-27T09:43:49Z

Hi Helge,

On Thu, 2025-11-27 at 10:25 +0100, John Paul Adrian Glaubitz wrote:
> Hi Helge,
>
> On Wed, 2025-11-26 at 21:15 +0100, Helge Deller wrote:
> > So, here is a (untested) v3:
> >
> >
> > [PATCH v3] apparmor: Optimize table creation from possibly unaligned memory
> >
> > Source blob may come from userspace and might be unaligned.
> > Try to optize the copying process by avoiding unaligned memory accesses.
> >
> > Signed-off-by: Helge Deller <deller@gmx.de>
> >
> > diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h
> > index 1fbe82f5021b..19e72b3e8f49 100644
> > --- a/security/apparmor/include/match.h
> > +++ b/security/apparmor/include/match.h
> > @@ -104,16 +104,18 @@ struct aa_dfa {
> > struct table_header *tables[YYTD_ID_TSIZE];
> > };
> >
> > -#define byte_to_byte(X) (X)
> > -
> > #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX) \
> > do { \
> > typeof(LEN) __i; \
> > TTYPE *__t = (TTYPE *) TABLE; \
> > BTYPE *__b = (BTYPE *) BLOB; \
> > - for (__i = 0; __i < LEN; __i++) { \
> > - __t[__i] = NTOHX(__b[__i]); \
> > - } \
> > + BUILD_BUG_ON(sizeof(TTYPE) != sizeof(BTYPE)); \
> > + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) \
> > + memcpy(__t, __b, (LEN) * sizeof(BTYPE)); \
> > + else /* copy & convert convert from big-endian */ \
> > + for (__i = 0; __i < LEN; __i++) { \
> > + __t[__i] = NTOHX(&__b[__i]); \
> > + } \
> > } while (0)
> >
> > static inline size_t table_size(size_t len, size_t el_size)
> > diff --git a/security/apparmor/match.c b/security/apparmor/match.c
> > index c5a91600842a..1e32c8ba14ae 100644
> > --- a/security/apparmor/match.c
> > +++ b/security/apparmor/match.c
> > @@ -15,6 +15,7 @@
> > #include <linux/vmalloc.h>
> > #include <linux/err.h>
> > #include <linux/kref.h>
> > +#include <linux/unaligned.h>
> >
> > #include "include/lib.h"
> > #include "include/match.h"
> > @@ -66,14 +67,13 @@ static struct table_header *unpack_table(char *blob, size_t bsize)
> > table->td_flags = th.td_flags;
> > table->td_lolen = th.td_lolen;
> > if (th.td_flags == YYTD_DATA8)
> > - UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
> > - u8, u8, byte_to_byte);
> > + memcpy(table->td_data, blob, th.td_lolen);
> > else if (th.td_flags == YYTD_DATA16)
> > UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
> > - u16, __be16, be16_to_cpu);
> > + u16, __be16, get_unaligned_be16);
> > else if (th.td_flags == YYTD_DATA32)
> > UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
> > - u32, __be32, be32_to_cpu);
> > + u32, __be32, get_unaligned_be32);
> > else
> > goto fail;
> > /* if table was vmalloced make sure the page tables are synced
>
> This one does not apply:
>
> glaubitz@node54:/data/home/glaubitz/linux> git am ../20251125_app_armor_unalign_2nd.mbx
> Applying: apparmor unaligned memory fixes
> error: patch failed: security/apparmor/match.c:15
> error: security/apparmor/match.c: patch does not apply
> Patch failed at 0001 apparmor unaligned memory fixes
> hint: Use 'git am --show-current-patch=diff' to see the failed patch
> hint: When you have resolved this problem, run "git am --continue".
> hint: If you prefer to skip this patch, run "git am --skip" instead.
> hint: To restore the original branch and stop patching, run "git am --abort".
> hint: Disable this message with "git config set advice.mergeConflict false"
> glaubitz@node54:/data/home/glaubitz/linux>

The patch alone applies, i.e without your previous patch, but it does not fix the problem:

[ 73.961582] Kernel unaligned access at TPC[8dabdc] aa_dfa_unpack+0x3c/0x6e0
[ 74.053195] Kernel unaligned access at TPC[8dabec] aa_dfa_unpack+0x4c/0x6e0
[ 74.144814] Kernel unaligned access at TPC[8dacd0] aa_dfa_unpack+0x130/0x6e0
[ 74.237538] Kernel unaligned access at TPC[8dacd0] aa_dfa_unpack+0x130/0x6e0
[ 74.330296] Kernel unaligned access at TPC[8dacd0] aa_dfa_unpack+0x130/0x6e0

Adrian

--
.''`. John Paul Adrian Glaubitz
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