Commit 1c1e618ddd15f69fd87ccea596769f78c8065504
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7855c35da7
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rlimits: allow setrlimit to non-current tasks
Add locking to allow setrlimit accept task parameter other than current. Namely, lock tasklist_lock for read and check whether the task structure has sighand non-null. Do all the signal processing under that lock still held. There are some points: 1) security_task_setrlimit is now called with that lock held. This is not new, many security_* functions are called with this lock held already so it doesn't harm (all this security_* stuff does almost the same). 2) task->sighand->siglock (in update_rlimit_cpu) is nested in tasklist_lock. This dependence is already existing. 3) tsk->alloc_lock is nested in tasklist_lock. This is OK too, already existing dependence. Signed-off-by: Jiri Slaby <jirislaby@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com>
Showing 1 changed file with 10 additions and 1 deletions Side-by-side Diff
kernel/sys.c
| ... | ... | @@ -1272,6 +1272,7 @@ |
| 1272 | 1272 | |
| 1273 | 1273 | #endif |
| 1274 | 1274 | |
| 1275 | +/* make sure you are allowed to change @tsk limits before calling this */ | |
| 1275 | 1276 | int do_setrlimit(struct task_struct *tsk, unsigned int resource, |
| 1276 | 1277 | struct rlimit *new_rlim) |
| 1277 | 1278 | { |
| 1278 | 1279 | |
| ... | ... | @@ -1285,9 +1286,16 @@ |
| 1285 | 1286 | if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open) |
| 1286 | 1287 | return -EPERM; |
| 1287 | 1288 | |
| 1289 | + /* protect tsk->signal and tsk->sighand from disappearing */ | |
| 1290 | + read_lock(&tasklist_lock); | |
| 1291 | + if (!tsk->sighand) { | |
| 1292 | + retval = -ESRCH; | |
| 1293 | + goto out; | |
| 1294 | + } | |
| 1295 | + | |
| 1288 | 1296 | retval = security_task_setrlimit(tsk->group_leader, resource, new_rlim); |
| 1289 | 1297 | if (retval) |
| 1290 | - return retval; | |
| 1298 | + goto out; | |
| 1291 | 1299 | |
| 1292 | 1300 | if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) { |
| 1293 | 1301 | /* |
| ... | ... | @@ -1322,6 +1330,7 @@ |
| 1322 | 1330 | |
| 1323 | 1331 | update_rlimit_cpu(tsk, new_rlim->rlim_cur); |
| 1324 | 1332 | out: |
| 1333 | + read_unlock(&tasklist_lock); | |
| 1325 | 1334 | return retval; |
| 1326 | 1335 | } |
| 1327 | 1336 |