[sr-dev] [kamailio/kamailio] cfg_rpc updates changing variable values to large random numbers (#1583)

I was trying to do a cfg_rpc update on a variable and some of the times, the variable would take on randomly large values or negative values. The -1 here is probably causing issues. https://github.com/kamailio/kamailio/blob/1d53ea3dba4e59b05b2e92ecc973c4415… Here's an explanation of what's going on (debugged using gdb). In cfg_struc.c if you put a breakpoint in the following line in cfg_clone_global https://github.com/kamailio/kamailio/blob/1d53ea3dba4e59b05b2e92ecc973c4415… checking variable values: ``` --- Old (correct) value --- (gdb) print sizeof(*(int *)(((unsigned char *)((*cfg_global)->vars + 984)) + 172)) $33 = 4 (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((*cfg_global)->vars + 984)) + 172)) + 0) $34 = 99 'c' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((*cfg_global)->vars + 984)) + 172)) + 1) $35 = 0 '\000' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((*cfg_global)->vars + 984)) + 172)) + 2) $36 = 0 '\000' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((*cfg_global)->vars + 984)) + 172)) + 3) $37 = 0 '\000' --- new (corrupt) value --- (gdb) print sizeof(*(int *)(((unsigned char *)((block)->vars + 984)) + 172)) $28 = 4 (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((block)->vars + 984)) + 172)) + 0) $29 = 99 'c' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((block)->vars + 984)) + 172)) + 1) $30 = 0 '\000' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((block)->vars + 984)) + 172)) + 2) $31 = 0 '\000' (gdb) print *((unsigned char *)&(*(int *)(((unsigned char *)((block)->vars + 984)) + 172)) + 3) $32 = 130 '\202' ``` As visible, the last byte is getting corrupted. I checked the memory allocation variables: ``` --> cfg_block_size (gdb) print cfg_block_size $2 = 1156 --> sizeof(cfg_block_t) print sizeof(cfg_block_t) $15 = 8 ``` This means that total memory assigned = 8 + 1156 -(1) = 1163 ``` --> address of new block (gdb) print (void *) block $12 = (void *) 0x7f63086b6758 --> address of the corrupted variable in the new block (gdb) print (void *)(((unsigned char *)((block)->vars + 984)) + 172) $13 = (void *) 0x7f63086b6be0 --> offset of the variable from the block start (gdb) print 0x7f63086b6be0 - 0x7f63086b6758 $14 = 1160 ``` since the variable is an integer, memory that should be assigned = 1160 + 4 = 1164 However, we're assigning 1163. Therefore the last byte is getting corrupted. Does it make sense to remove the -1 from all the memory allocation in cfg_struct ? -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/kamailio/kamailio/issues/1583