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FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Score: -3.01 X-Spam-Flag: NO On 11/14/24 14:34, Hyeonggon Yoo wrote: > On Thu, Oct 17, 2024 at 12:42 AM Feng Tang wrote: >> >> For current krealloc(), one problem is its caller doesn't pass the old >> request size, say the object is 64 bytes kmalloc one, but caller may >> only requested 48 bytes. Then when krealloc() shrinks or grows in the >> same object, or allocate a new bigger object, it lacks this 'original >> size' information to do accurate data preserving or zeroing (when >> __GFP_ZERO is set). >> >> Thus with slub debug redzone and object tracking enabled, parts of the >> object after krealloc() might contain redzone data instead of zeroes, >> which is violating the __GFP_ZERO guarantees. Good thing is in this >> case, kmalloc caches do have this 'orig_size' feature. So solve the >> problem by utilize 'org_size' to do accurate data zeroing and preserving. >> >> [Thanks to syzbot and V, Narasimhan for discovering kfence and big >> kmalloc related issues in early patch version] >> >> Suggested-by: Vlastimil Babka >> Signed-off-by: Feng Tang >> --- >> mm/slub.c | 84 +++++++++++++++++++++++++++++++++++++++---------------- >> 1 file changed, 60 insertions(+), 24 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 1d348899f7a3..958f7af79fad 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -4718,34 +4718,66 @@ static __always_inline __realloc_size(2) void * >> __do_krealloc(const void *p, size_t new_size, gfp_t flags) >> { >> void *ret; >> - size_t ks; >> - >> - /* Check for double-free before calling ksize. */ >> - if (likely(!ZERO_OR_NULL_PTR(p))) { >> - if (!kasan_check_byte(p)) >> - return NULL; >> - ks = ksize(p); >> - } else >> - ks = 0; >> - >> - /* If the object still fits, repoison it precisely. */ >> - if (ks >= new_size) { >> - /* Zero out spare memory. */ >> - if (want_init_on_alloc(flags)) { >> - kasan_disable_current(); >> + size_t ks = 0; >> + int orig_size = 0; >> + struct kmem_cache *s = NULL; >> + >> + /* Check for double-free. */ >> + if (unlikely(ZERO_OR_NULL_PTR(p))) >> + goto alloc_new; > > nit: I think kasan_check_bytes() is the function that checks for double-free? Hm yeah, moved the comment. > Otherwise looks good to me, > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Thanks!