strlim: avoid one-byte stack overflow #7408
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Since the limit is up to 500 characters, make sure to allocate 501
bytes, including the terminator at the end, avoiding the stack overflow:
data.table::fread(text = paste0(
strrep("mary had a little lamb\n", 100),
strrep("a", 500), "\n", "a")
)
==5358==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffd0f20c7e4 at pc 0x7f06826bb311 bp 0x7ffd0f20ad90 sp 0x7ffd0f20ad88
WRITE of size 1 at 0x7ffd0f20c7e4 thread T0
#0 0x7f06826bb310 in strlim /tmp/RtmpvbbbcM/R.INSTALLd607e4c6707/data.table/src/fread.c:235
#1 0x7f06826bb310 in freadMain /tmp/RtmpvbbbcM/R.INSTALLd607e4c6707/data.table/src/fread.c:2947
#2 0x7f06826c2d62 in freadR /tmp/RtmpvbbbcM/R.INSTALLd607e4c6707/data.table/src/freadR.c:229
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #7408 +/- ##
=======================================
Coverage 99.13% 99.13%
=======================================
Files 85 85
Lines 16610 16618 +8
=======================================
+ Hits 16466 16474 +8
Misses 144 144 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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No obvious timing issues in HEAD=strlim-overflow Generated via commit 53ccb07 Download link for the artifact containing the test results: ↓ atime-results.zip
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Member
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Would the simple example you shared be useful in the test suite? data.table::fread(text = paste0(
strrep("mary had a little lamb\n", 100),
strrep("a", 500), "\n", "a")
) |
MichaelChirico
approved these changes
Nov 3, 2025
Member
I guess not since the error only surfaces with ASAN IINM |
Contributor
Author
|
We have AddressSanitizer in GitLab CI. I don't mind adding a test if it is warranted. |
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Since the limit is up to 500 characters, make sure to allocate 501 bytes, including the terminator at the end, avoiding the stack overflow introduced in #7005:
Will this need a test? By itself the overflow is probably harmless, as it only writes a single zero into a place on the stack that doesn't seem to be used by anything, but it trips up sanitizers before other crashes can be reproduced, for example:
...eventually: