37 lines
1.2 KiB
Diff
37 lines
1.2 KiB
Diff
From c3c41d4ffbdbbce2e7199ece8f76cea0310de820 Mon Sep 17 00:00:00 2001
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From: Theodore Ts'o <tytso@mit.edu>
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Date: Thu, 21 Jan 2021 23:27:00 -0500
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Subject: [PATCH] libext2fs: fix UBSAN warning in ext2fs_mmp_new_seq()
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Left shifting the pid by 16 bits can cause a UBSAN warning if the pid
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is greater than or equal to 2**16. It doesn't matter since we're just
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using the pid to seed for a pseudo-random number generator, but
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silence the warning by just swapping the high and low 16 bits of the
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pid instead.
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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---
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lib/ext2fs/mmp.c | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/lib/ext2fs/mmp.c b/lib/ext2fs/mmp.c
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index e96a2273..223b617d 100644
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--- a/lib/ext2fs/mmp.c
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+++ b/lib/ext2fs/mmp.c
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@@ -172,9 +172,11 @@ unsigned ext2fs_mmp_new_seq(void)
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#ifdef CONFIG_MMP
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unsigned new_seq;
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struct timeval tv;
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+ unsigned long pid = getpid();
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gettimeofday(&tv, 0);
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- srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
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+ pid = (pid >> 16) | ((pid & 0xFFFF) << 16);
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+ srand(pid ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
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gettimeofday(&tv, 0);
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/* Crank the random number generator a few times */
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--
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2.25.1
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