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From d61ff409cb4dda31386373d706ea0cfb1aaac5b7 Mon Sep 17 00:00:00 2001
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From: Jens Axboe <axboe@kernel.dk>
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Date: Wed, 2 May 2018 10:24:17 -0600
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Subject: [PATCH] btt: make device/devno use PATH_MAX to avoid overflow
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Herbo Zhang reports:
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I found a bug in blktrace/btt/devmap.c. The code is just as follows:
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https://git.kernel.org/pub/scm/linux/kernel/git/axboe/blktrace.git/tree/btt/devmap.c?id=8349ad2f2d19422a6241f94ea84d696b21de4757
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struct devmap {
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struct list_head head;
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char device[32], devno[32]; // #1
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};
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LIST_HEAD(all_devmaps);
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static int dev_map_add(char *line)
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{
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struct devmap *dmp;
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if (strstr(line, "Device") != NULL)
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return 1;
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dmp = malloc(sizeof(struct devmap));
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if (sscanf(line, "%s %s", dmp->device, dmp->devno) != 2) { //#2
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free(dmp);
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return 1;
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}
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list_add_tail(&dmp->head, &all_devmaps);
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return 0;
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}
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int dev_map_read(char *fname)
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{
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char line[256]; // #3
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FILE *fp = my_fopen(fname, "r");
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if (!fp) {
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perror(fname);
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return 1;
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}
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while (fscanf(fp, "%255[a-zA-Z0-9 :.,/_-]\n", line) == 1) {
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if (dev_map_add(line))
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break;
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}
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fclose(fp);
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return 0;
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}
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The line length is 256, but the dmp->device, dmp->devno max length
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is only 32. We can put strings longer than 32 into dmp->device and
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dmp->devno , and then they will be overflowed.
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we can trigger this bug just as follows:
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$ python -c "print 'A'*256" > ./test
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$ btt -M ./test
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*** Error in btt': free(): invalid next size (fast): 0x000055ad7349b250 ***
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======= Backtrace: =========
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/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7f7f158ce7e5]
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/lib/x86_64-linux-gnu/libc.so.6(+0x7fe0a)[0x7f7f158d6e0a]
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/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f7f158da98c]
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btt(+0x32e0)[0x55ad7306f2e0]
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btt(+0x2c5f)[0x55ad7306ec5f]
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btt(+0x251f)[0x55ad7306e51f]
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/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7f7f15877830]
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btt(+0x26b9)[0x55ad7306e6b9]
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======= Memory map: ========
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55ad7306c000-55ad7307f000 r-xp 00000000 08:14 3698139
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/usr/bin/btt
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55ad7327e000-55ad7327f000 r--p 00012000 08:14 3698139
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/usr/bin/btt
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55ad7327f000-55ad73280000 rw-p 00013000 08:14 3698139
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/usr/bin/btt
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55ad73280000-55ad73285000 rw-p 00000000 00:00 0
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55ad7349a000-55ad734bb000 rw-p 00000000 00:00 0
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[heap]
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7f7f10000000-7f7f10021000 rw-p 00000000 00:00 0
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7f7f10021000-7f7f14000000 ---p 00000000 00:00 0
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7f7f15640000-7f7f15656000 r-xp 00000000 08:14 14942237
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/lib/x86_64-linux-gnu/libgcc_s.so.1
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7f7f15656000-7f7f15855000 ---p 00016000 08:14 14942237
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/lib/x86_64-linux-gnu/libgcc_s.so.1
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7f7f15855000-7f7f15856000 r--p 00015000 08:14 14942237
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/lib/x86_64-linux-gnu/libgcc_s.so.1
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7f7f15856000-7f7f15857000 rw-p 00016000 08:14 14942237
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/lib/x86_64-linux-gnu/libgcc_s.so.1
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7f7f15857000-7f7f15a16000 r-xp 00000000 08:14 14948477
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/lib/x86_64-linux-gnu/libc-2.23.so
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7f7f15a16000-7f7f15c16000 ---p 001bf000 08:14 14948477
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/lib/x86_64-linux-gnu/libc-2.23.so
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7f7f15c16000-7f7f15c1a000 r--p 001bf000 08:14 14948477
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/lib/x86_64-linux-gnu/libc-2.23.so
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7f7f15c1a000-7f7f15c1c000 rw-p 001c3000 08:14 14948477
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/lib/x86_64-linux-gnu/libc-2.23.so
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7f7f15c1c000-7f7f15c20000 rw-p 00000000 00:00 0
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7f7f15c20000-7f7f15c46000 r-xp 00000000 08:14 14948478
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/lib/x86_64-linux-gnu/ld-2.23.so
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7f7f15e16000-7f7f15e19000 rw-p 00000000 00:00 0
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7f7f15e42000-7f7f15e45000 rw-p 00000000 00:00 0
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7f7f15e45000-7f7f15e46000 r--p 00025000 08:14 14948478
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/lib/x86_64-linux-gnu/ld-2.23.so
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7f7f15e46000-7f7f15e47000 rw-p 00026000 08:14 14948478
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/lib/x86_64-linux-gnu/ld-2.23.so
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7f7f15e47000-7f7f15e48000 rw-p 00000000 00:00 0
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7ffdebe5c000-7ffdebe7d000 rw-p 00000000 00:00 0
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[stack]
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7ffdebebc000-7ffdebebe000 r--p 00000000 00:00 0
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[vvar]
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7ffdebebe000-7ffdebec0000 r-xp 00000000 00:00 0
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[vdso]
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ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0
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[vsyscall]
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[1] 6272 abort btt -M test
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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---
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btt/devmap.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/btt/devmap.c b/btt/devmap.c
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index 0553a9e..5fc1cb2 100644
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--- a/btt/devmap.c
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+++ b/btt/devmap.c
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@@ -23,7 +23,7 @@
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struct devmap {
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struct list_head head;
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- char device[32], devno[32];
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+ char device[PATH_MAX], devno[PATH_MAX];
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};
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LIST_HEAD(all_devmaps);
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--
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2.9.5
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