The patch titled Subject: lib/idr.c: fix out-of-bounds pointer dereference has been added to the -mm tree. Its filename is lib-idr-fix-out-of-bounds-pointer-dereference.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/lib-idr-fix-out-of-bounds-pointer-dereference.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/lib-idr-fix-out-of-bounds-pointer-dereference.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> Subject: lib/idr.c: fix out-of-bounds pointer dereference I'm working on address sanitizer project for kernel. Recently we started experiments with stack instrumentation, to detect out-of-bounds read/write bugs on stack. Just after booting I've hit out-of-bounds read on stack in idr_for_each (and in __idr_remove_all as well): struct idr_layer **paa = &pa[0]; while (id >= 0 && id <= max) { ... while (n < fls(id)) { n += IDR_BITS; p = *--paa; <--- here we are reading pa[-1] value. } } Despite the fact that after this dereference we are exiting out of loop and never use p, such behaviour is undefined and should be avoided. Fix this by moving pointer derference to the beggining of the loop, right before we will use it. Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Alexey Preobrazhensky <preobr@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/idr.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff -puN lib/idr.c~lib-idr-fix-out-of-bounds-pointer-dereference lib/idr.c --- a/lib/idr.c~lib-idr-fix-out-of-bounds-pointer-dereference +++ a/lib/idr.c @@ -590,26 +590,27 @@ static void __idr_remove_all(struct idr struct idr_layer **paa = &pa[0]; n = idp->layers * IDR_BITS; - p = idp->top; + *paa = idp->top; RCU_INIT_POINTER(idp->top, NULL); max = idr_max(idp->layers); id = 0; while (id >= 0 && id <= max) { + p = *paa; while (n > IDR_BITS && p) { n -= IDR_BITS; - *paa++ = p; p = p->ary[(id >> n) & IDR_MASK]; + *++paa = p; } bt_mask = id; id += 1 << n; /* Get the highest bit that the above add changed from 0->1. */ while (n < fls(id ^ bt_mask)) { - if (p) - free_layer(idp, p); + if (*paa) + free_layer(idp, *paa); n += IDR_BITS; - p = *--paa; + --paa; } } idp->layers = 0; @@ -692,15 +693,16 @@ int idr_for_each(struct idr *idp, struct idr_layer **paa = &pa[0]; n = idp->layers * IDR_BITS; - p = rcu_dereference_raw(idp->top); + *paa = rcu_dereference_raw(idp->top); max = idr_max(idp->layers); id = 0; while (id >= 0 && id <= max) { + p = *paa; while (n > 0 && p) { n -= IDR_BITS; - *paa++ = p; p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); + *++paa = p; } if (p) { @@ -712,7 +714,7 @@ int idr_for_each(struct idr *idp, id += 1 << n; while (n < fls(id)) { n += IDR_BITS; - p = *--paa; + --paa; } } @@ -740,17 +742,18 @@ void *idr_get_next(struct idr *idp, int int n, max; /* find first ent */ - p = rcu_dereference_raw(idp->top); + p = *paa = rcu_dereference_raw(idp->top); if (!p) return NULL; n = (p->layer + 1) * IDR_BITS; max = idr_max(p->layer + 1); while (id >= 0 && id <= max) { + p = *paa; while (n > 0 && p) { n -= IDR_BITS; - *paa++ = p; p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); + *++paa = p; } if (p) { @@ -768,7 +771,7 @@ void *idr_get_next(struct idr *idp, int id = round_up(id + 1, 1 << n); while (n < fls(id)) { n += IDR_BITS; - p = *--paa; + --paa; } } return NULL; _ Patches currently in -mm which might be from a.ryabinin@xxxxxxxxxxx are mm-slabh-wrap-the-whole-file-with-guarding-macro.patch mm-slub-slub_debug=n-use-the-same-alloc-free-hooks-as-for-slub_debug=y.patch lib-idr-fix-out-of-bounds-pointer-dereference.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html