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5oN4qcdk0rmR-KiMS2gj92P9ohUePXdg Hi I, thanks for looking into the syzbot report. On Mon, Sep 22, 2025 at 10:33:57PM +0530, I Viswanath wrote: > syzbot reported WARNING in max_vclocks_store. > > This occurs when the size argument fits into a u32 but is too large > to allocate, i.e., when it's between KMALLOC_MAX_SIZE + 1 > and UINT_MAX (both limits included) This is not quite. When bytes > KKMALLOC_MAX_SIZE (8K on my system), kmalloc redirects allocation to the buddy allocator, which can allocate up to (PAGE_SIZE << MAX_PAGE_ORDER) bytes (4M on my system). Because allocating a page with order > MAX_PAGE_ORDER page is never supposed to succeed, the caller of kmalloc should be fixed rather than kmalloc itself. > Add validation to kmalloc_array_noprof() and related functions to > return early if the requested size exceeds KMALLOC_MAX_SIZE. This is against the point of WARNING in the buddy allocator. I think the right fix should be to return -EINVAL in max_vclocks_store() if max * sizeof(int) exceeds PAGE_SIZE << MAX_PAGE_ORDER? -- Cheers, Harry / Hyeonggon > This seems like the most reasonable place for this guard. > > Would it be a good idea to move the check down to > the lower level functions like __kmalloc_node_noprof()? > > Moving it up is not a good idea because > max_vclocks_store shouldn't reason around KMALLOC_MAX_SIZE, > a mm specific macro. > > Should the Fixes: commit here be the one in which this file > was added? > > Reported-by: syzbot+94d20db923b9f51be0df@syzkaller.appspotmail.com > Tested-by: syzbot+94d20db923b9f51be0df@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=94d20db923b9f51be0df > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: I Viswanath > --- > include/linux/slab.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index d5a8ab98035c..6db15c5b2ce7 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -943,7 +943,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_noprof(size_t n, size_t siz > { > size_t bytes; > > - if (unlikely(check_mul_overflow(n, size, &bytes))) > + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_SIZE))) > return NULL; > return kmalloc_noprof(bytes, flags); > } > @@ -973,7 +973,7 @@ static inline __realloc_size(2, 3) void * __must_check krealloc_array_noprof(voi > { > size_t bytes; > > - if (unlikely(check_mul_overflow(new_n, new_size, &bytes))) > + if (unlikely(check_mul_overflow(new_n, new_size, &bytes) || (bytes > KMALLOC_MAX_SIZE))) > return NULL; > > return krealloc_noprof(p, bytes, flags); > @@ -1013,7 +1013,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_node_noprof(size_t n, size_ > { > size_t bytes; > > - if (unlikely(check_mul_overflow(n, size, &bytes))) > + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_SIZE))) > return NULL; > if (__builtin_constant_p(n) && __builtin_constant_p(size)) > return kmalloc_node_noprof(bytes, flags, node); > @@ -1059,7 +1059,7 @@ kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node) > { > size_t bytes; > > - if (unlikely(check_mul_overflow(n, size, &bytes))) > + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_SIZE))) > return NULL; > > return kvmalloc_node_noprof(bytes, flags, node); > -- > 2.47.3 >