Commit 6ff2d39b91aec3dcae951afa982059e3dd9b49dc
Committed by
Linus Torvalds
Linus Torvalds
1 parent
1d678f365d
Exists in
master
and in
4 other branches
lib/idr.c: fix rcu related race with idr_find
2nd part of the fixes needed for http://bugzilla.kernel.org/show_bug.cgi?id=11796. When the idr tree is either grown or shrunk, then the update to the number of layers and the top pointer were not atomic. This race caused crashes. The attached patch fixes that by replicating the layers counter in each layer, thus idr_find doesn't need idp->layers anymore. Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Clement Calmels <cboulte@gmail.com> Cc: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Pierre Peiffer <peifferp@gmail.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 2 changed files with 14 additions and 3 deletions Side-by-side Diff
include/linux/idr.h
| ... | ... | @@ -52,13 +52,14 @@ |
| 52 | 52 | unsigned long bitmap; /* A zero bit means "space here" */ |
| 53 | 53 | struct idr_layer *ary[1<<IDR_BITS]; |
| 54 | 54 | int count; /* When zero, we can release it */ |
| 55 | + int layer; /* distance from leaf */ | |
| 55 | 56 | struct rcu_head rcu_head; |
| 56 | 57 | }; |
| 57 | 58 | |
| 58 | 59 | struct idr { |
| 59 | 60 | struct idr_layer *top; |
| 60 | 61 | struct idr_layer *id_free; |
| 61 | - int layers; | |
| 62 | + int layers; /* only valid without concurrent changes */ | |
| 62 | 63 | int id_free_cnt; |
| 63 | 64 | spinlock_t lock; |
| 64 | 65 | }; |
lib/idr.c
| ... | ... | @@ -185,6 +185,7 @@ |
| 185 | 185 | new = get_from_free_list(idp); |
| 186 | 186 | if (!new) |
| 187 | 187 | return -1; |
| 188 | + new->layer = l-1; | |
| 188 | 189 | rcu_assign_pointer(p->ary[m], new); |
| 189 | 190 | p->count++; |
| 190 | 191 | } |
| ... | ... | @@ -210,6 +211,7 @@ |
| 210 | 211 | if (unlikely(!p)) { |
| 211 | 212 | if (!(p = get_from_free_list(idp))) |
| 212 | 213 | return -1; |
| 214 | + p->layer = 0; | |
| 213 | 215 | layers = 1; |
| 214 | 216 | } |
| 215 | 217 | /* |
| ... | ... | @@ -237,6 +239,7 @@ |
| 237 | 239 | } |
| 238 | 240 | new->ary[0] = p; |
| 239 | 241 | new->count = 1; |
| 242 | + new->layer = layers-1; | |
| 240 | 243 | if (p->bitmap == IDR_FULL) |
| 241 | 244 | __set_bit(0, &new->bitmap); |
| 242 | 245 | p = new; |
| 243 | 246 | |
| 244 | 247 | |
| 245 | 248 | |
| ... | ... | @@ -493,17 +496,21 @@ |
| 493 | 496 | int n; |
| 494 | 497 | struct idr_layer *p; |
| 495 | 498 | |
| 496 | - n = idp->layers * IDR_BITS; | |
| 497 | 499 | p = rcu_dereference(idp->top); |
| 500 | + if (!p) | |
| 501 | + return NULL; | |
| 502 | + n = (p->layer+1) * IDR_BITS; | |
| 498 | 503 | |
| 499 | 504 | /* Mask off upper bits we don't use for the search. */ |
| 500 | 505 | id &= MAX_ID_MASK; |
| 501 | 506 | |
| 502 | 507 | if (id >= (1 << n)) |
| 503 | 508 | return NULL; |
| 509 | + BUG_ON(n == 0); | |
| 504 | 510 | |
| 505 | 511 | while (n > 0 && p) { |
| 506 | 512 | n -= IDR_BITS; |
| 513 | + BUG_ON(n != p->layer*IDR_BITS); | |
| 507 | 514 | p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]); |
| 508 | 515 | } |
| 509 | 516 | return((void *)p); |
| 510 | 517 | |
| ... | ... | @@ -582,8 +589,11 @@ |
| 582 | 589 | int n; |
| 583 | 590 | struct idr_layer *p, *old_p; |
| 584 | 591 | |
| 585 | - n = idp->layers * IDR_BITS; | |
| 586 | 592 | p = idp->top; |
| 593 | + if (!p) | |
| 594 | + return ERR_PTR(-EINVAL); | |
| 595 | + | |
| 596 | + n = (p->layer+1) * IDR_BITS; | |
| 587 | 597 | |
| 588 | 598 | id &= MAX_ID_MASK; |
| 589 | 599 |