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Groups > linux.kernel > #1736140
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v3 04/31] dcache: Define usercopy region in dentry_cache slab cache |
| Date | 2017-09-20 23:10 +0200 |
| Message-ID | <urUpP-8nU-11@gated-at.bofh.it> (permalink) |
| References | <urU6t-818-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: David Windsor <dave@nullcore.net>
When a dentry name is short enough, it can be stored directly in the
dentry itself (instead in a separate kmalloc allocation). These dentry
short names, stored in struct dentry.d_iname and therefore contained in
the dentry_cache slab cache, need to be coped to userspace.
cache object allocation:
fs/dcache.c:
__d_alloc(...):
...
dentry = kmem_cache_alloc(dentry_cache, ...);
...
dentry->d_name.name = dentry->d_iname;
example usage trace:
filldir+0xb0/0x140
dcache_readdir+0x82/0x170
iterate_dir+0x142/0x1b0
SyS_getdents+0xb5/0x160
fs/readdir.c:
(called via ctx.actor by dir_emit)
filldir(..., const char *name, ...):
...
copy_to_user(..., name, namlen)
fs/libfs.c:
dcache_readdir(...):
...
next = next_positive(dentry, p, 1)
...
dir_emit(..., next->d_name.name, ...)
In support of usercopy hardening, this patch defines a region in the
dentry_cache slab cache in which userspace copy operations are allowed.
This region is known as the slab cache's usercopy region. Slab caches can
now check that each copy operation involving cache-managed memory falls
entirely within the slab's usercopy region.
This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.
Signed-off-by: David Windsor <dave@nullcore.net>
[kees: adjust hunks for kmalloc-specific things moved later]
[kees: adjust commit log, provide usage trace]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/dcache.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index f90141387f01..5f5e7c1fcf4b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3603,8 +3603,9 @@ static void __init dcache_init(void)
* but it is probably not worth it because of the cache nature
* of the dcache.
*/
- dentry_cache = KMEM_CACHE(dentry,
- SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT);
+ dentry_cache = KMEM_CACHE_USERCOPY(dentry,
+ SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
+ d_iname);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
--
2.7.4
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[PATCH v3 00/31] Hardened usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 22:50 +0200
[PATCH v3 26/31] fork: Provide usercopy whitelisting for task_struct Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 15/31] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 07/31] ext4: Define usercopy region in ext4_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 29/31] arm: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 25/31] fork: Define usercopy region in thread_stack slab caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 02/31] usercopy: Enforce slab cache usercopy region boundaries Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
Re: [PATCH v3 02/31] usercopy: Enforce slab cache usercopy region boundaries Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
[PATCH v3 23/31] net: Restrict unwhitelisted proto caches to size 0 Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 17/31] scsi: Define usercopy region in scsi_sense_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 19/31] ip: Define usercopy region in IP proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 28/31] arm64: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 21/31] sctp: Define usercopy region in SCTP proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 31/31] lkdtm: Update usercopy tests for whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 01/31] usercopy: Prepare for usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
Re: [PATCH v3 01/31] usercopy: Prepare for usercopy whitelisting Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
[PATCH v3 08/31] ext2: Define usercopy region in ext2_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 18/31] net: Define usercopy region in struct proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 24/31] fork: Define usercopy region in mm_struct slab caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
[PATCH v3 04/31] dcache: Define usercopy region in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
[PATCH v3 27/31] x86: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
[PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-21 17:50 +0200
Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Christopher Lameter <cl@linux.com> - 2017-09-21 18:10 +0200
Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-21 20:30 +0200
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