| Message ID | ZjDXY74yS6UyQPxv@archlinux (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] slub: Fixes freepointer encoding for single free | expand |
On 4/30/24 1:34 PM, Nicolas Bouchinet wrote: > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > Commit 284f17ac13fe ("mm/slub: handle bulk and single object freeing > separately") splits single and bulk object freeing in two functions > slab_free() and slab_free_bulk() which leads slab_free() to call > slab_free_hook() directly instead of slab_free_freelist_hook(). > > If `init_on_free` is set, slab_free_hook() zeroes the object. > Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` are > set, the do_slab_free() slowpath executes freelist consistency > checks and try to decode a zeroed freepointer which leads to a > "Freepointer corrupt" detection in check_object(). > > During bulk free, slab_free_freelist_hook() isn't affected as it always > sets it objects freepointer using set_freepointer() to maintain its > reconstructed freelist after `init_on_free`. > > For single free, object's freepointer thus needs to be avoided when > stored outside the object if `init_on_free` is set. The freepointer left > as is, check_object() may later detect an invalid pointer value due to > objects overflow. > > To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the > command line of a kernel build with `CONFIG_SLAB_FREELIST_HARDENED=y`. > > dmesg sample log: > [ 10.708715] ============================================================================= > [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): Freepointer corrupt > [ 10.712695] ----------------------------------------------------------------------------- > [ 10.712695] > [ 10.712695] Slab 0xffffd8bdc400d580 objects=32 used=4 fp=0xffff9d9a80356f80 flags=0x200000000000a00(workingset|slab|node=0|zone=2) > [ 10.716698] Object 0xffff9d9a80356600 @offset=1536 fp=0x7ee4f480ce0ecd7c > [ 10.716698] > [ 10.716698] Bytes b4 ffff9d9a803565f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356610: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035666c: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035667c: 00 00 00 00 .... > [ 10.724696] FIX kmalloc-rnd-05-32: Object at 0xffff9d9a80356600 not freed > > Co-developed-by: Chengming Zhou <chengming.zhou@linux.dev> Chengming Zhou, could you provide your s-o-b please? > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> Added to slab/for-6.9-rc7/fixes, thanks!
On 2024/4/30 19:58, Vlastimil Babka wrote: > On 4/30/24 1:34 PM, Nicolas Bouchinet wrote: >> From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> >> >> Commit 284f17ac13fe ("mm/slub: handle bulk and single object freeing >> separately") splits single and bulk object freeing in two functions >> slab_free() and slab_free_bulk() which leads slab_free() to call >> slab_free_hook() directly instead of slab_free_freelist_hook(). >> >> If `init_on_free` is set, slab_free_hook() zeroes the object. >> Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` are >> set, the do_slab_free() slowpath executes freelist consistency >> checks and try to decode a zeroed freepointer which leads to a >> "Freepointer corrupt" detection in check_object(). >> >> During bulk free, slab_free_freelist_hook() isn't affected as it always >> sets it objects freepointer using set_freepointer() to maintain its >> reconstructed freelist after `init_on_free`. >> >> For single free, object's freepointer thus needs to be avoided when >> stored outside the object if `init_on_free` is set. The freepointer left >> as is, check_object() may later detect an invalid pointer value due to >> objects overflow. >> >> To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the >> command line of a kernel build with `CONFIG_SLAB_FREELIST_HARDENED=y`. >> >> dmesg sample log: >> [ 10.708715] ============================================================================= >> [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): Freepointer corrupt >> [ 10.712695] ----------------------------------------------------------------------------- >> [ 10.712695] >> [ 10.712695] Slab 0xffffd8bdc400d580 objects=32 used=4 fp=0xffff9d9a80356f80 flags=0x200000000000a00(workingset|slab|node=0|zone=2) >> [ 10.716698] Object 0xffff9d9a80356600 @offset=1536 fp=0x7ee4f480ce0ecd7c >> [ 10.716698] >> [ 10.716698] Bytes b4 ffff9d9a803565f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> [ 10.720703] Object ffff9d9a80356600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> [ 10.720703] Object ffff9d9a80356610: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> [ 10.724696] Padding ffff9d9a8035666c: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> [ 10.724696] Padding ffff9d9a8035667c: 00 00 00 00 .... >> [ 10.724696] FIX kmalloc-rnd-05-32: Object at 0xffff9d9a80356600 not freed >> >> Co-developed-by: Chengming Zhou <chengming.zhou@linux.dev> > > Chengming Zhou, could you provide your s-o-b please? Of course. Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> > >> Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > Added to slab/for-6.9-rc7/fixes, thanks! Thanks!
Hi Nicolas, > Subject: [PATCH v3] slub: Fixes freepointer encoding for single free > With slub_debug=FUZ init_on_free=1 loglevel=7, I see error In 6.6 kernel. Should this patch be backported to 6.6? I also had a hack together with your patch applied to 6.6 diff --git a/mm/slub.c b/mm/slub.c index 96406f9813e8..ff8cdc737722 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1209,7 +1209,8 @@ static int check_object(struct kmem_cache *s, struct slab *slab, if (s->object_size > orig_size && !check_bytes_and_report(s, slab, object, "kmalloc Redzone", p + orig_size, - val, s->object_size - orig_size)) { + slab_want_init_on_free(s) ? 0 : val, + s->object_size - orig_size)) { return 0; } } Thanks, Peng. > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > Commit 284f17ac13fe ("mm/slub: handle bulk and single object > freeing > separately") splits single and bulk object freeing in two functions > slab_free() and slab_free_bulk() which leads slab_free() to call > slab_free_hook() directly instead of slab_free_freelist_hook(). > > If `init_on_free` is set, slab_free_hook() zeroes the object. > Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` > are set, the do_slab_free() slowpath executes freelist consistency > checks and try to decode a zeroed freepointer which leads to a > "Freepointer corrupt" detection in check_object(). > > During bulk free, slab_free_freelist_hook() isn't affected as it always > sets it objects freepointer using set_freepointer() to maintain its > reconstructed freelist after `init_on_free`. > > For single free, object's freepointer thus needs to be avoided when > stored outside the object if `init_on_free` is set. The freepointer left as > is, check_object() may later detect an invalid pointer value due to > objects overflow. > > To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the > command line of a kernel build with > `CONFIG_SLAB_FREELIST_HARDENED=y`. > > dmesg sample log: > [ 10.708715] > ============================================================ > ================= > [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): > Freepointer corrupt > [ 10.712695] ----------------------------------------------------------------------------- > [ 10.712695] > [ 10.712695] Slab 0xffffd8bdc400d580 objects=32 used=4 > fp=0xffff9d9a80356f80 > flags=0x200000000000a00(workingset|slab|node=0|zone=2) > [ 10.716698] Object 0xffff9d9a80356600 @offset=1536 > fp=0x7ee4f480ce0ecd7c > [ 10.716698] > [ 10.716698] Bytes b4 ffff9d9a803565f0: 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356600: 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356610: 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035666c: 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035667c: 00 00 00 > 00 .... > [ 10.724696] FIX kmalloc-rnd-05-32: Object at 0xffff9d9a80356600 > not freed > > Co-developed-by: Chengming Zhou <chengming.zhou@linux.dev> > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > --- > Changes since v2: > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F > lore.kernel.org%2Fall%2FZjCxZfD1d36zfq- > R%40archlinux%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C38af > dff178a0422aeddc08dc690996f5%7C686ea1d3bc2b4c6fa92cd99c5c3 > 01635%7C0%7C0%7C638500737122575573%7CUnknown%7CTWFpb > GZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC > JXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=Q4Vs38E%2F7HSIETGC2hYD > 07gN6U8hkVZR764Yn4TFWlw%3D&reserved=0 > > * Reword commit message in order to clarify the patch approach as > suggested by Vlastimil Babka > > Changes since v1: > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F > lore.kernel.org%2Fall%2FZij_fGjRS_rK- > 65r%40archlinux%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C38 > afdff178a0422aeddc08dc690996f5%7C686ea1d3bc2b4c6fa92cd99c5c > 301635%7C0%7C0%7C638500737122594077%7CUnknown%7CTWFp > bGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiL > CJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=xWgnIygCHwUPjnFENutIai > cMTk0HQTne8hQfOqIzbA0%3D&reserved=0 > > * Jump above out of object freepointer if init_on_free is set instead of > initializing it with set_freepointer() as suggested by Vlastimil Babka. > > * Adapt maybe_wipe_obj_freeptr() to avoid wiping out of object on > alloc freepointer as suggested by Chengming Zhou. > > * Reword commit message. > --- > mm/slub.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 3aa12b9b323d..173c340ec1d3 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2102,15 +2102,20 @@ bool slab_free_hook(struct kmem_cache > *s, void *x, bool init) > * > * The initialization memset's clear the object and the > metadata, > * but don't touch the SLAB redzone. > + * > + * The object's freepointer is also avoided if stored outside the > + * object. > */ > if (unlikely(init)) { > int rsize; > + unsigned int inuse; > > + inuse = get_info_end(s); > if (!kasan_has_integrated_init()) > memset(kasan_reset_tag(x), 0, s->object_size); > rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad : > 0; > - memset((char *)kasan_reset_tag(x) + s->inuse, 0, > - s->size - s->inuse - rsize); > + memset((char *)kasan_reset_tag(x) + inuse, 0, > + s->size - inuse - rsize); > } > /* KASAN might put x into memory quarantine, delaying its > reuse. */ > return !kasan_slab_free(s, x, init); > @@ -3789,7 +3794,7 @@ static void *__slab_alloc_node(struct > kmem_cache *s, static __always_inline void > maybe_wipe_obj_freeptr(struct kmem_cache *s, > void *obj) > { > - if (unlikely(slab_want_init_on_free(s)) && obj) > + if (unlikely(slab_want_init_on_free(s)) && obj && > +!freeptr_outside_object(s)) > memset((void *)((char *)kasan_reset_tag(obj) + s- > >offset), > 0, sizeof(void *)); > } > -- > 2.44.0 >
On 8/19/24 04:43, Peng Fan wrote: > Hi Nicolas, >> Subject: [PATCH v3] slub: Fixes freepointer encoding for single free >> > > With slub_debug=FUZ init_on_free=1 loglevel=7, I see error > In 6.6 kernel. Should this patch be backported to 6.6? But it was a fix for commit 284f17ac13fe that's from 6.8 and wasn't backported to 6.6. Are you seeing the same error happening for the same reason, or is it a different one? > I also had a hack together with your patch applied to 6.6 > diff --git a/mm/slub.c b/mm/slub.c > index 96406f9813e8..ff8cdc737722 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1209,7 +1209,8 @@ static int check_object(struct kmem_cache *s, struct slab *slab, > if (s->object_size > orig_size && > !check_bytes_and_report(s, slab, object, > "kmalloc Redzone", p + orig_size, > - val, s->object_size - orig_size)) { > + slab_want_init_on_free(s) ? 0 : val, > + s->object_size - orig_size)) { > return 0; > } > } > > Thanks, > Peng. > >> From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> >> >> Commit 284f17ac13fe ("mm/slub: handle bulk and single object >> freeing >> separately") splits single and bulk object freeing in two functions >> slab_free() and slab_free_bulk() which leads slab_free() to call >> slab_free_hook() directly instead of slab_free_freelist_hook(). >> >> If `init_on_free` is set, slab_free_hook() zeroes the object. >> Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` >> are set, the do_slab_free() slowpath executes freelist consistency >> checks and try to decode a zeroed freepointer which leads to a >> "Freepointer corrupt" detection in check_object(). >> >> During bulk free, slab_free_freelist_hook() isn't affected as it always >> sets it objects freepointer using set_freepointer() to maintain its >> reconstructed freelist after `init_on_free`. >> >> For single free, object's freepointer thus needs to be avoided when >> stored outside the object if `init_on_free` is set. The freepointer left as >> is, check_object() may later detect an invalid pointer value due to >> objects overflow. >> >> To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the >> command line of a kernel build with >> `CONFIG_SLAB_FREELIST_HARDENED=y`. >> >> dmesg sample log: >> [ 10.708715] >> ============================================================ >> ================= >> [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): >> Freepointer corrupt >> [ 10.712695] ----------------------------------------------------------------------------- >> [ 10.712695] >> [ 10.712695] Slab 0xffffd8bdc400d580 objects=32 used=4 >> fp=0xffff9d9a80356f80 >> flags=0x200000000000a00(workingset|slab|node=0|zone=2) >> [ 10.716698] Object 0xffff9d9a80356600 @offset=1536 >> fp=0x7ee4f480ce0ecd7c >> [ 10.716698] >> [ 10.716698] Bytes b4 ffff9d9a803565f0: 00 00 00 00 00 00 00 00 00 >> 00 00 00 00 00 00 00 ................ >> [ 10.720703] Object ffff9d9a80356600: 00 00 00 00 00 00 00 00 00 >> 00 00 00 00 00 00 00 ................ >> [ 10.720703] Object ffff9d9a80356610: 00 00 00 00 00 00 00 00 00 >> 00 00 00 00 00 00 00 ................ >> [ 10.724696] Padding ffff9d9a8035666c: 00 00 00 00 00 00 00 00 00 >> 00 00 00 00 00 00 00 ................ >> [ 10.724696] Padding ffff9d9a8035667c: 00 00 00 >> 00 .... >> [ 10.724696] FIX kmalloc-rnd-05-32: Object at 0xffff9d9a80356600 >> not freed >> >> Co-developed-by: Chengming Zhou <chengming.zhou@linux.dev> >> Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> >> --- >> Changes since v2: >> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F >> lore.kernel.org%2Fall%2FZjCxZfD1d36zfq- >> R%40archlinux%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C38af >> dff178a0422aeddc08dc690996f5%7C686ea1d3bc2b4c6fa92cd99c5c3 >> 01635%7C0%7C0%7C638500737122575573%7CUnknown%7CTWFpb >> GZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC >> JXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=Q4Vs38E%2F7HSIETGC2hYD >> 07gN6U8hkVZR764Yn4TFWlw%3D&reserved=0 >> >> * Reword commit message in order to clarify the patch approach as >> suggested by Vlastimil Babka >> >> Changes since v1: >> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F >> lore.kernel.org%2Fall%2FZij_fGjRS_rK- >> 65r%40archlinux%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C38 >> afdff178a0422aeddc08dc690996f5%7C686ea1d3bc2b4c6fa92cd99c5c >> 301635%7C0%7C0%7C638500737122594077%7CUnknown%7CTWFp >> bGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiL >> CJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=xWgnIygCHwUPjnFENutIai >> cMTk0HQTne8hQfOqIzbA0%3D&reserved=0 >> >> * Jump above out of object freepointer if init_on_free is set instead of >> initializing it with set_freepointer() as suggested by Vlastimil Babka. >> >> * Adapt maybe_wipe_obj_freeptr() to avoid wiping out of object on >> alloc freepointer as suggested by Chengming Zhou. >> >> * Reword commit message. >> --- >> mm/slub.c | 11 ++++++++--- >> 1 file changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 3aa12b9b323d..173c340ec1d3 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -2102,15 +2102,20 @@ bool slab_free_hook(struct kmem_cache >> *s, void *x, bool init) >> * >> * The initialization memset's clear the object and the >> metadata, >> * but don't touch the SLAB redzone. >> + * >> + * The object's freepointer is also avoided if stored outside the >> + * object. >> */ >> if (unlikely(init)) { >> int rsize; >> + unsigned int inuse; >> >> + inuse = get_info_end(s); >> if (!kasan_has_integrated_init()) >> memset(kasan_reset_tag(x), 0, s->object_size); >> rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad : >> 0; >> - memset((char *)kasan_reset_tag(x) + s->inuse, 0, >> - s->size - s->inuse - rsize); >> + memset((char *)kasan_reset_tag(x) + inuse, 0, >> + s->size - inuse - rsize); >> } >> /* KASAN might put x into memory quarantine, delaying its >> reuse. */ >> return !kasan_slab_free(s, x, init); >> @@ -3789,7 +3794,7 @@ static void *__slab_alloc_node(struct >> kmem_cache *s, static __always_inline void >> maybe_wipe_obj_freeptr(struct kmem_cache *s, >> void *obj) >> { >> - if (unlikely(slab_want_init_on_free(s)) && obj) >> + if (unlikely(slab_want_init_on_free(s)) && obj && >> +!freeptr_outside_object(s)) >> memset((void *)((char *)kasan_reset_tag(obj) + s- >> >offset), >> 0, sizeof(void *)); >> } >> -- >> 2.44.0 >> >
diff --git a/mm/slub.c b/mm/slub.c index 3aa12b9b323d..173c340ec1d3 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2102,15 +2102,20 @@ bool slab_free_hook(struct kmem_cache *s, void *x, bool init) * * The initialization memset's clear the object and the metadata, * but don't touch the SLAB redzone. + * + * The object's freepointer is also avoided if stored outside the + * object. */ if (unlikely(init)) { int rsize; + unsigned int inuse; + inuse = get_info_end(s); if (!kasan_has_integrated_init()) memset(kasan_reset_tag(x), 0, s->object_size); rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad : 0; - memset((char *)kasan_reset_tag(x) + s->inuse, 0, - s->size - s->inuse - rsize); + memset((char *)kasan_reset_tag(x) + inuse, 0, + s->size - inuse - rsize); } /* KASAN might put x into memory quarantine, delaying its reuse. */ return !kasan_slab_free(s, x, init); @@ -3789,7 +3794,7 @@ static void *__slab_alloc_node(struct kmem_cache *s, static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, void *obj) { - if (unlikely(slab_want_init_on_free(s)) && obj) + if (unlikely(slab_want_init_on_free(s)) && obj && !freeptr_outside_object(s)) memset((void *)((char *)kasan_reset_tag(obj) + s->offset), 0, sizeof(void *)); }