Re: [PATCH V4] Fix NULL dereference in super_by_fd

[Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>]

On Wed, 21 Dec 2022 17:37:52 +0800
Li Xiao Keng <lixiaokeng@huawei.com> wrote:

> When we create 100 partitions (major is 259 not 254) in a raid device,
> mdadm may coredump:
> 
> Core was generated by `/usr/sbin/mdadm --detail --export /dev/md1p7'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  __strlen_avx2_rtm () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:74
> 74		VPCMPEQ	(%rdi), %ymm0, %ymm1
> (gdb) bt
> #0  __strlen_avx2_rtm () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:74
> #1  0x00007fbb9a7e4139 in __strcpy_chk (dest=dest@entry=0x55d55d6a13ac "",
> src=0x0, destlen=destlen@entry=32) at strcpy_chk.c:28 #2  0x000055d55ba1766d
> in strcpy (__src=<optimized out>, __dest=0x55d55d6a13ac "") at
> /usr/include/bits/string_fortified.h:79 #3  super_by_fd (fd=fd@entry=3,
> subarrayp=subarrayp@entry=0x7fff44dfcc48) at util.c:1289 #4
> 0x000055d55ba273a6 in Detail (dev=0x7fff44dfef0b "/dev/md1p7",
> c=0x7fff44dfe440) at Detail.c:101 #5  0x000055d55ba0de61 in misc_list
> (c=<optimized out>, ss=<optimized out>, dump_directory=<optimized out>,
> ident=<optimized out>, devlist=<optimized out>) at mdadm.c:1959 #6  main
> (argc=<optimized out>, argv=<optimized out>) at mdadm.c:1629
> 
> The direct cause is fd2devnm returning NULL, so add a check.
> 
> V1->V2: When fd2devnm return NULL, super_by_fd return NULL but not an
> incomplete 'st' entry. At the same time, add a check in map_by_devnm
> to avoid coredump.
> 
> V2->V3: Fix style issues.
> V3->V4: Change strcpy() to strncpy().
> 
> Signed-off-by: Li Xiao Keng <lixiaokeng@huawei.com>
> Signed-off-by: Wu Guang Hao <wuguanghao3@huawei.com>


Acked-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>

Coly could you please take a look?

Thanks,
Mariusz