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Full Discussion: Problem about Kernel oops
Top Forums Programming Problem about Kernel oops Post 302588173 by homeboy on Saturday 7th of January 2012 08:39:39 AM
Old 01-07-2012
Problem about Kernel oops

hello,everyone,I'm reading LDD3.Topics about oops,it said the code bellow would cause a fault condition because "this method copies a string to a local variable,unfortunately,the string is longer than the destination array".Well,hard to understand....Is that right?I thought the fault should be caused by the wrong memset,it overwrite the function stack,the value of __user is 0xff now.will anyone tell me what happened here?Thanks;
Code:
size_t fauly_read(struct file *filp, char __user *buf, size_t count, loff_t *pos)
{
      int ret;
      char stack_buf[4];

      memset(stack_buf, 0xff, 20);
      if(count > 4)
           count  = 4;

      ret = copy_to_user(buf, stack_buf, count);
      if(!ret)
          return count;

      return ret;
}

 

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abrt_dump_oops_selinux(8)				   SELinux Policy abrt_dump_oops				 abrt_dump_oops_selinux(8)

NAME
abrt_dump_oops_selinux - Security Enhanced Linux Policy for the abrt_dump_oops processes DESCRIPTION
Security-Enhanced Linux secures the abrt_dump_oops processes via flexible mandatory access control. The abrt_dump_oops processes execute with the abrt_dump_oops_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier. For example: ps -eZ | grep abrt_dump_oops_t ENTRYPOINTS
The abrt_dump_oops_t SELinux type can be entered via the abrt_dump_oops_exec_t file type. The default entrypoint paths for the abrt_dump_oops_t domain are the following: /usr/bin/abrt-dump-oops, /usr/bin/abrt-uefioops-oops PROCESS TYPES
SELinux defines process types (domains) for each process running on the system You can see the context of a process using the -Z option to ps Policy governs the access confined processes have to files. SELinux abrt_dump_oops policy is very flexible allowing users to setup their abrt_dump_oops processes in as secure a method as possible. The following process types are defined for abrt_dump_oops: abrt_dump_oops_t Note: semanage permissive -a abrt_dump_oops_t can be used to make the process type abrt_dump_oops_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. BOOLEANS
SELinux policy is customizable based on least access required. abrt_dump_oops policy is extremely flexible and has several booleans that allow you to manipulate the policy and run abrt_dump_oops with the tightest access possible. If you want to allow all daemons the ability to read/write terminals, you must turn on the daemons_use_tty boolean. Disabled by default. setsebool -P daemons_use_tty 1 If you want to deny any process from ptracing or debugging any other processes, you must turn on the deny_ptrace boolean. Enabled by default. setsebool -P deny_ptrace 1 If you want to allow all domains to use other domains file descriptors, you must turn on the domain_fd_use boolean. Enabled by default. setsebool -P domain_fd_use 1 If you want to allow all domains to have the kernel load modules, you must turn on the domain_kernel_load_modules boolean. Disabled by default. setsebool -P domain_kernel_load_modules 1 If you want to allow all domains to execute in fips_mode, you must turn on the fips_mode boolean. Enabled by default. setsebool -P fips_mode 1 If you want to enable reading of urandom for all domains, you must turn on the global_ssp boolean. Disabled by default. setsebool -P global_ssp 1 MANAGED FILES
The SELinux process type abrt_dump_oops_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note the processes UID still need to have DAC permissions. abrt_var_cache_t /var/tmp/abrt(/.*)? /var/cache/abrt(/.*)? /var/spool/abrt(/.*)? /var/spool/debug(/.*)? /var/cache/abrt-di(/.*)? /var/spool/rhsm/debug(/.*)? FILE CONTEXTS
SELinux requires files to have an extended attribute to define the file type. You can see the context of a file using the -Z option to ls Policy governs the access confined processes have to these files. SELinux abrt_dump_oops policy is very flexible allowing users to setup their abrt_dump_oops processes in as secure a method as possible. STANDARD FILE CONTEXT SELinux defines the file context types for the abrt_dump_oops, if you wanted to store files with these types in a diffent paths, you need to execute the semanage command to sepecify alternate labeling and then use restorecon to put the labels on disk. semanage fcontext -a -t abrt_dump_oops_exec_t '/srv/abrt_dump_oops/content(/.*)?' restorecon -R -v /srv/myabrt_dump_oops_content Note: SELinux often uses regular expressions to specify labels that match multiple files. The following file types are defined for abrt_dump_oops: abrt_dump_oops_exec_t - Set files with the abrt_dump_oops_exec_t type, if you want to transition an executable to the abrt_dump_oops_t domain. Paths: /usr/bin/abrt-dump-oops, /usr/bin/abrt-uefioops-oops Note: File context can be temporarily modified with the chcon command. If you want to permanently change the file context you need to use the semanage fcontext command. This will modify the SELinux labeling database. You will need to use restorecon to apply the labels. COMMANDS
semanage fcontext can also be used to manipulate default file context mappings. semanage permissive can also be used to manipulate whether or not a process type is permissive. semanage module can also be used to enable/disable/install/remove policy modules. semanage boolean can also be used to manipulate the booleans system-config-selinux is a GUI tool available to customize SELinux policy settings. AUTHOR
This manual page was auto-generated using sepolicy manpage . SEE ALSO
selinux(8), abrt_dump_oops(8), semanage(8), restorecon(8), chcon(1), sepolicy(8) , setsebool(8) abrt_dump_oops 14-06-10 abrt_dump_oops_selinux(8)
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