[PATCH] ldb: Fix index out of bound in ldb_msg_find_common_values

[Douglas Bagnall]

On 06/07/17 01:33, Lukas Slebodnik wrote:
> ehlo,
> 
> I noticed failure[1] when I was packaging libldb-1.2.0 to fedora
> which was required for samba-4.7.0rc1. And I was quite lucky that
> it failed at least for i386 :-)
> 
> I did not noticed it with 1.1.31 because unit tests were not executed as part
> of build due to other issues.
> 

Thanks Lukas!


> LS
> 
> [1] https://koji.fedoraproject.org/koji/taskinfo?taskID=20322524
> 
> 
> 0001-ldb-Fix-index-out-of-bound-in-ldb_msg_find_common_va.patch
> 
> 
> From 68e9da7bc4049b1a2080d07324cc26eebe5ee55b Mon Sep 17 00:00:00 2001
> From: Lukas Slebodnik <lslebodn at redhat.com>
> Date: Tue, 4 Jul 2017 15:46:49 +0200
> Subject: [PATCH] ldb: Fix index out of bound in ldb_msg_find_common_values
> 
> cmocka unit test failed on i386
> [==========] Running 2 test(s).
> [ RUN      ] test_ldb_msg_find_duplicate_val
> [       OK ] test_ldb_msg_find_duplicate_val
> [ RUN      ] test_ldb_msg_find_common_values
> [  FAILED  ] test_ldb_msg_find_common_values
> [==========] 2 test(s) run.
> [  ERROR   ] --- 0x14 != 0
> [   LINE   ] --- ../tests/ldb_msg.c:266: error: Failure!
> [  PASSED  ] 1 test(s).
> [  FAILED  ] 1 test(s), listed below:
> [  FAILED  ] test_ldb_msg_find_common_values
>  1 FAILED TEST(S)
> 
> But we were just lucky on other platforms because there is
> index out of bound according to valgrind error.
> 
> ==3298== Invalid read of size 4
> ==3298==    at 0x486FCF6: ldb_val_cmp (ldb_msg.c:95)
> ==3298==    by 0x486FCF6: ldb_msg_find_common_values (ldb_msg.c:266)
> ==3298==    by 0x109A3D: test_ldb_msg_find_common_values (ldb_msg.c:265)
> ==3298==    by 0x48E7490: ??? (in /usr/lib/libcmocka.so.0.4.1)
> ==3298==    by 0x48E7EB0: _cmocka_run_group_tests (in /usr/lib/libcmocka.so.0.4.1)
> ==3298==    by 0x1089B7: main (ldb_msg.c:352)
> ==3298==  Address 0x4b07734 is 4 bytes after a block of size 48 alloc'd
> ==3298==    at 0x483223E: malloc (vg_replace_malloc.c:299)
> ==3298==    by 0x4907AA7: _talloc_array (in /usr/lib/libtalloc.so.2.1.9)
> ==3298==    by 0x486FBF8: ldb_msg_find_common_values (ldb_msg.c:245)
> ==3298==    by 0x109A3D: test_ldb_msg_find_common_values (ldb_msg.c:265)
> ==3298==    by 0x48E7490: ??? (in /usr/lib/libcmocka.so.0.4.1)
> ==3298==    by 0x48E7EB0: _cmocka_run_group_tests (in /usr/lib/libcmocka.so.0.4.1)
> ==3298==    by 0x1089B7: main (ldb_msg.c:352)
> 
> Signed-off-by: Lukas Slebodnik <lslebodn at redhat.com>
> ---
>  lib/ldb/common/ldb_msg.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/lib/ldb/common/ldb_msg.c b/lib/ldb/common/ldb_msg.c
> index abad5a8320551c09e64539b993b8c5408ccdd32a..8e4047b41beebcadeab9631bc820941f0eadc490 100644
> --- a/lib/ldb/common/ldb_msg.c
> +++ b/lib/ldb/common/ldb_msg.c
> @@ -262,20 +262,12 @@ int ldb_msg_find_common_values(struct ldb_context *ldb,
>  	n_values = el->num_values;
>  	i = 0;
>  	j = 0;
> -	while (i != n_values) {
> +	while (i != n_values && j < el2->num_values) {
>  		int ret = ldb_val_cmp(&values[i], &values2[j]);
>  		if (ret < 0) {
>  			i++;
>  		} else if (ret > 0) {
>  			j++;
> -			if (j == el2->num_values) {

The problem was when el2 has no values, right? In which case we really
don't want to be here to start with. Which I obviously failed to check
and to test.

We also need something like the attached patch. And a test or two, which
I'll get onto.

thanks,
Douglas

> -				/*
> -				  We have walked past the end of the second
> -				  list, meaning the remainder of the first
> -				  list cannot collide and we're done.
> -				*/
> -				break;
> -			}
>  		} else {
>  			/* we have a collision */
>  			if (! remove_duplicates) {
> -- 2.13.0
> 

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