| Message ID | 20220201034915.183117-2-dgilbert@interlog.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | scatterlist: add new capabilities | expand |
On Mon, Jan 31, 2022 at 10:49:12PM -0500, Douglas Gilbert wrote: > This patch fixes a check done by sgl_alloc_order() before it starts > any allocations. The comment in the original said: "Check for integer > overflow" but the right hand side of the expression in the condition > is resolved as u32 so it can not exceed UINT32_MAX (4 GiB) which > means 'length' can not exceed that value. > > This function may be used to replace vmalloc(unsigned long) for a > large allocation (e.g. a ramdisk). vmalloc has no limit at 4 GiB so > it seems unreasonable that sgl_alloc_order() whose length type is > unsigned long long should be limited to 4 GB. > > In early 2021 there was discussion between Jason Gunthorpe > <jgg@ziepe.ca> and Bodo Stroesser <bostroesser@gmail.com> about the > way to check for overflow caused by order (an exponent) being > too large. Take the solution proposed by Bodo in post dated > 20210118 to the linux-scsi and linux-block lists. > > An earlier patch fixed a memory leak in sg_alloc_order() due to the > misuse of sgl_free(). Take the opportunity to put a one line comment > above sgl_free()'s declaration warning that it is not suitable when > order > 0 . > > Cc: Jason Gunthorpe <jgg@ziepe.ca> > Reviewed-by: Bodo Stroesser <bostroesser@gmail.com> > Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> > --- > include/linux/scatterlist.h | 1 + > lib/scatterlist.c | 24 +++++++++++++----------- > 2 files changed, 14 insertions(+), 11 deletions(-) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index 7ff9d6386c12..03130be581bb 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -357,6 +357,7 @@ struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, > unsigned int *nent_p); > void sgl_free_n_order(struct scatterlist *sgl, int nents, int order); > void sgl_free_order(struct scatterlist *sgl, int order); > +/* Only use sgl_free() when order is 0 */ > void sgl_free(struct scatterlist *sgl); > #endif /* CONFIG_SGL_ALLOC */ > > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index d5e82e4a57ad..ed6d0465c78e 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -585,13 +585,16 @@ EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); > #ifdef CONFIG_SGL_ALLOC > > /** > - * sgl_alloc_order - allocate a scatterlist and its pages > + * sgl_alloc_order - allocate a scatterlist with equally sized elements each > + * of which has 2^@order continuous pages > * @length: Length in bytes of the scatterlist. Must be at least one > - * @order: Second argument for alloc_pages() > + * @order: Second argument for alloc_pages(). Each sgl element size will > + * be (PAGE_SIZE*2^@order) bytes. @order must not exceed 16. > * @chainable: Whether or not to allocate an extra element in the scatterlist > - * for scatterlist chaining purposes > + * for scatterlist chaining purposes > * @gfp: Memory allocation flags > - * @nent_p: [out] Number of entries in the scatterlist that have pages > + * @nent_p: [out] Number of entries in the scatterlist that have pages. > + * Ignored if @nent_p is NULL. > * > * Returns: A pointer to an initialized scatterlist or %NULL upon failure. > */ > @@ -604,16 +607,15 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, > unsigned int nent, nalloc; > u32 elem_len; > > - nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); > - /* Check for integer overflow */ > - if (length > (nent << (PAGE_SHIFT + order))) > + if (length >> (PAGE_SHIFT + order) >= UINT_MAX) > return NULL; > - nalloc = nent; > + nent = DIV_ROUND_UP(length, PAGE_SIZE << order); > + This would be clearer to make nent/etc an unsigned long long. Then check if nalloc is > SIZE_MAX before casting it to size_t for the allocation. Avoids the wonky if statement. Kaspm
Hi Douglas,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on linus/master]
[also build test ERROR on v5.17-rc2 next-20220131]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Douglas-Gilbert/scatterlist-add-new-capabilities/20220201-115047
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 26291c54e111ff6ba87a164d85d4a4e134b7315c
config: i386-randconfig-a003-20220131 (https://download.01.org/0day-ci/archive/20220201/202202012125.JGVcLupw-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/be1e80a043970c400c00709be739ab26f931331a
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Douglas-Gilbert/scatterlist-add-new-capabilities/20220201-115047
git checkout be1e80a043970c400c00709be739ab26f931331a
# save the config file to linux build tree
mkdir build_dir
make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
ld: lib/scatterlist.o: in function `sgl_alloc_order':
>> lib/scatterlist.c:612: undefined reference to `__udivdi3'
vim +612 lib/scatterlist.c
586
587 /**
588 * sgl_alloc_order - allocate a scatterlist with equally sized elements each
589 * of which has 2^@order continuous pages
590 * @length: Length in bytes of the scatterlist. Must be at least one
591 * @order: Second argument for alloc_pages(). Each sgl element size will
592 * be (PAGE_SIZE*2^@order) bytes. @order must not exceed 16.
593 * @chainable: Whether or not to allocate an extra element in the scatterlist
594 * for scatterlist chaining purposes
595 * @gfp: Memory allocation flags
596 * @nent_p: [out] Number of entries in the scatterlist that have pages.
597 * Ignored if @nent_p is NULL.
598 *
599 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
600 */
601 struct scatterlist *sgl_alloc_order(unsigned long long length,
602 unsigned int order, bool chainable,
603 gfp_t gfp, unsigned int *nent_p)
604 {
605 struct scatterlist *sgl, *sg;
606 struct page *page;
607 unsigned int nent, nalloc;
608 u32 elem_len;
609
610 if (length >> (PAGE_SHIFT + order) >= UINT_MAX)
611 return NULL;
> 612 nent = DIV_ROUND_UP(length, PAGE_SIZE << order);
613
614 if (chainable) {
615 if (check_add_overflow(nent, 1U, &nalloc))
616 return NULL;
617 } else {
618 nalloc = nent;
619 }
620 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
621 gfp & ~GFP_DMA);
622 if (!sgl)
623 return NULL;
624
625 sg_init_table(sgl, nalloc);
626 sg = sgl;
627 while (length) {
628 elem_len = min_t(u64, length, PAGE_SIZE << order);
629 page = alloc_pages(gfp, order);
630 if (!page) {
631 sgl_free_order(sgl, order);
632 return NULL;
633 }
634
635 sg_set_page(sg, page, elem_len, 0);
636 length -= elem_len;
637 sg = sg_next(sg);
638 }
639 WARN_ONCE(length, "length = %lld\n", length);
640 if (nent_p)
641 *nent_p = nent;
642 return sgl;
643 }
644 EXPORT_SYMBOL(sgl_alloc_order);
645
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 7ff9d6386c12..03130be581bb 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -357,6 +357,7 @@ struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, unsigned int *nent_p); void sgl_free_n_order(struct scatterlist *sgl, int nents, int order); void sgl_free_order(struct scatterlist *sgl, int order); +/* Only use sgl_free() when order is 0 */ void sgl_free(struct scatterlist *sgl); #endif /* CONFIG_SGL_ALLOC */ diff --git a/lib/scatterlist.c b/lib/scatterlist.c index d5e82e4a57ad..ed6d0465c78e 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -585,13 +585,16 @@ EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); #ifdef CONFIG_SGL_ALLOC /** - * sgl_alloc_order - allocate a scatterlist and its pages + * sgl_alloc_order - allocate a scatterlist with equally sized elements each + * of which has 2^@order continuous pages * @length: Length in bytes of the scatterlist. Must be at least one - * @order: Second argument for alloc_pages() + * @order: Second argument for alloc_pages(). Each sgl element size will + * be (PAGE_SIZE*2^@order) bytes. @order must not exceed 16. * @chainable: Whether or not to allocate an extra element in the scatterlist - * for scatterlist chaining purposes + * for scatterlist chaining purposes * @gfp: Memory allocation flags - * @nent_p: [out] Number of entries in the scatterlist that have pages + * @nent_p: [out] Number of entries in the scatterlist that have pages. + * Ignored if @nent_p is NULL. * * Returns: A pointer to an initialized scatterlist or %NULL upon failure. */ @@ -604,16 +607,15 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, unsigned int nent, nalloc; u32 elem_len; - nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); - /* Check for integer overflow */ - if (length > (nent << (PAGE_SHIFT + order))) + if (length >> (PAGE_SHIFT + order) >= UINT_MAX) return NULL; - nalloc = nent; + nent = DIV_ROUND_UP(length, PAGE_SIZE << order); + if (chainable) { - /* Check for integer overflow */ - if (nalloc + 1 < nalloc) + if (check_add_overflow(nent, 1U, &nalloc)) return NULL; - nalloc++; + } else { + nalloc = nent; } sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), gfp & ~GFP_DMA);